ECU/MAFS Problems
Breakdowns, Symptoms, Cure, Cost
For a discount on the cost of your MAFS repair see below for details.
Breakdowns, Symptoms, Cure, Cost
For a discount on the cost of your MAFS repair see below for details.
This page gives details of a breakdown experienced with this vehicle, along with the
Cause, History, Cure, & Cost.
* October 24th 2005. 'Mobilo-life' called due to stalling and rough running ECM (Engine Control Module) (Hand book ref.= Engine diagnosis Indicator lamp) was lit.
'Mobilo-life's' diagnostic's detected a defective oxygen sensor, located in the catalytic converter,
History
*Engine running normally, stalls on approach to roundabout,
* rolling re-start no problem, engine sounds rough,
* No dash warning lights at this point.
* Stopped for twenty minutes engine re-starts no problem,
* 500 yards engine sounds rough, acceleration erratic
* Engine Control Module lamp illuminates on dash display.
*Engine sounds as if is misfiring,
* black smoke omitting from exhaust thereby giving an indication that the fuel to mixture ratio is incorrect. * Engine continued to run and I made it home 1.5 miles away.
Initial diagnosed Cause
There are two oxygen sensors both of similar appearance the one nearest the engine
1
is the one which the 'Mobilo-life' technician diagnostic equipment says has failed.
The car was booked into an Independent Mercedes-Benz specialist www.mercedesj-a-haynes and I got an appointment for the repair to be carried out 4 days later during which time I did not use the car, However when the appointed garage tried to order the part, only the sensor at the back of catalytic converter was available. 2 The other is only available on a special order from Mercedes-Benz and the reason why it is required has to be specified along with chassis number etc, as it is not normal for it need replacement!
Action the garage therefore purchased the sensor available, (the sensor at the back of the cat. 2 Part Number A 002 540 01 17 (cost £149.69 inc (26/10/05
Availability of 02 sensors at greatly reduced prices.
For supply of replacement 02 sensors Lambda Sensors see page 34 09/06/09
this information was kindly provided by Tony, a fellow owner.
I digressed for good reason at that point because Mercedes Are now charging well over £150 per sensor.
However When I got the car out of my garage on the appointed day it started as normal and ran fine, although the engine management light was still displayed.
I arrived and left the car for the garage to fit the oxygen sensor and clear the fault, however when I returned I was told they had discovered further but related reasons as to why the ECM light was lit. a second diagnostic test had revealed that the mass air flow sensor had gone defective.
However if you have what appears to be a MAF Sensor problem Check that the air filter has been installed correctly and that the filter has been fully housed with filter lock fully slid into position this can cause the same symptoms as a MAFS defect as the air coming in the filter housing by passes the filter and flow direct to the MAF sensor.
These components ECM ( engine control module A and MAFS ( mass air flow sensor) B are integrated on the 'A' Class and therefore a fault developing one ,required them both to be replaced, at considerable cost, £764.05 plus VAT making a total bill of £897.76, a lot of anybodies money and I'm not amused.
I paid the garage for their time, diagnostic test and the part they had purchased on my behalf, they not being able to return it to MB Brighton, and in view of the fact that the car was still running normally drove it to my usual MB Garage, Main Dealer, who seeing the diagnostic sheet from the Independent Mercedes-Specialist confirmed that the fault was the Mass Air Flow Sensor.( MAFS) I had little choice but to order a ECM/MAFS combined unit which was going to take about 5 days to arrive, it being coded to my car at the factory
Having received this confirmed diagnoses I got the MB Garage to contact MB and ask them for a goodwill payment towards this cost, I received a direct refusal on parts and labour.
Having now driven some 50 + miles without a problem, apart from the ECM light showing on the dash display I still wasn't confident that the information I was being given was correct, and as I'd had to pay for the oxygen sensor I decided to fit it.
I then attended my local garage, the owner of whom I've known for years, he did an omissions test for me and the car was fine and would easily have passed an MOT. I then went back to the Specialist Mercedes Garage and asked them to delete the fault and then road test, sure enough the ECM light re-appeared after about few minutes of driving. That confirmed conclusively that it wasn't the sensor but that the fault was positively in the ECM/MAF. sensor.
This photo shows the crankcase breather pipe 1 interconnected with the pipe work of the ECU/MAFS, 2 this can be found full of oil/water brown emulsion, as shown below, and is best cleaned out before an oil change if, and when the need arises.
This small sample
3 is typical of the oil/water brown emulsion that can be found in the neck of the oil filler and also the crankcase breather pipe, more often than not caused by too many short runs where the engine is not able to reach its full operating temperature. Where this is a particular problem it is advisable to use engine flush prior to replacing the engine oil. The example in this photograph is nothing to worry about, although it was causing the owner some concern. I have seen much worse, a good long run and an oil change will normally deal with the problem.
In any circumstances if the oil is changed at the prescribed intervals , not more than twelve months there will be no problem,
Do not confuse this problem with a leaking head gasket unless you are having to regularly top up the coolant header tank with fluid.
It was interesting to see the difference in the old and the new sensors , why the change in design I don't know I just hope it is for the good of the car and that Mercedes-Benz aren't using the 'A' Class as a test bed!
I now contacted Mercedes Customer Services myself and explained the full scenario along with faxing them paperwork to substantiate that the wrong diagnoses/fault had been made and what it had cost me, as a result of my phone call Mercedes-Benz are going to reimburse me the £150.00 cost of the oxygen sensor.
Today 3 11 05 I have had the New ECM/MAFS fitted and asked for a diagnostic report showing that the New ECM/MAFS is fully functional and that the are no faults on the car at all.
I cant say that the car runs any different, a little smoother perhaps. But of course the ECM fault lamp has been extinguished, in truth I think the car is quieter running obviously due to the fuel/air mixture.
It is said that as you get older you get wiser! Well in this case it is true, since spending a great deal of money on my own car I have researched and am able to recommend two companies that will reliably repair the MAFS portion of the ECU/MAFS integrated unit fitted to the 'A' class, and ECU testing will undertake repairs to the ECU portion as well Great news as previously this has required a £1300 replacement unit from Mercedes-Benz, Germany, in both cases the companies place a two year warrantee on their repairs which is at least as long as Mercedes Benz New components.
Now I'm not only sharing this information with you but have arranged discounts with both companies so I hope the failure of your MAFS or now the ECU is not so traumatic and costly as mine .
Please do not confuse either of the companies below with this seller ashley1987-2008( 22) who is now advertising on E-Bay. I have no knowledge of the seller, and no discounts have been arranged. also note the repair is only guaranteed for a period of one year.
Remember if you choose to use one of the companies below for your repair, you will get a 15% discount if you mention my site 'Lofty's Homepage' or 'aclassinfo.co.uk' when placing your order, ,it will not be given automatically, other owners do not get this discount it is a perk arranged by lofty and very generously allowed by the companies mentioned to my readers in the case of both companies they offer a quick turn around and return of your repaired unit.
BBA Reman.co, location Rochester Kent. Telephone 0044-(0)1634-687222
The cost, £220 + carriage + Vat
Test only £35.00 + carriage + VAT.
Repairs undertaken by this Company are guaranteed for two years.
Please see my notes at the bottom of this page before making a decision as to which Company to use for the repair of your ECU/MAFS.
ECU Testing.com, Location, Derbyshire.Tel.0044(0)1773535638 or 07971468585
Business hours 9am to 6pm Monday to Friday, Location Derbyshire. will test and repair the MAFS integral of the ECU Cost £220
Please note THEY WILL ALSO UNDERTAKE REPAIRS TO THE ECU So if your in doubt as to whether your problem/fault is caused by either the MAFS or the ECU portion of your unit I would advise you to send it to them, they will be able to repair which ever is found to be faulty, if on test they find a repair is not required/necessary they will only charge £35.00 for handling, if you prefer to telephone, have the details of your ECU/MAFS to hand
Repairs undertaken by this Company are guaranteed for two years.
Hi there Lofty,
Just dropping you a line to say well done on the website, whenever we get anyone asking us how to remove there Mercedes A Class ECU/MAF we always direct them to your website. Every customer that reads it has commented how good your descriptions are and we are giving a lot of customers there 15% discount for mentioning your site.
There should be more sites like yours and you well deserve to do very well with it.
Kind regards
Roger & everyone at www.ecutesting.com
So there you have it, not only do they keep to their word and do a good job , they also appreciate your business and show it.
Hi Lofty, Just want to say thanks for all the info on your site. I had trouble with my MAFS so sent it off to ECU Testing. Phoned them on Mon and sent MAFS on Mon afternoon, it was returned by Wed morning and only cost £265 which is better than £1400 that two garages wanted. Also got 15% discount for mentioning your site. So thank you again. Gary.
Unquote
lets hope more readers will take this route when you encounter problems with your MAFS with a 15% discount can't be bad I wishes I known about my site when mine went !! sadly it wasn't written
For owners living abroad, One of my readers has used this company for his rebuild, you won't get information on how to remove fit etc but you have that info on this site, he paid 300€ and is very happy with the repair. www.actronics.nl Discounting is not arranged with this company.
Owners please be aware, if your car goes defective with a MAFS problem and is taken to a Mercedes garage for repairs MB will fit a new unit without question they will not want you having it repaired even though the warrantee period is greater than their new unit, so be on your guard you are the customer, it's your car tell them what your want done and stick to your guns or pay Six (6) times more for the new unit, fitted, the latest cost of New Mercedes -Benz ECU/MAFS sensor, fitted was £1400
There is no doubt that this monolith of MAFS/ECU combined is a complex unit, if you intend having it repaired then it is best left alone , this does not prevent you inspecting the reeds as this can be done by carefully the sleeve from the induction tube of the unit, see below
The latest information 10/04/09 reference Mercedes Costs for replacement and Fitting to one owner was £1400 approx, that's £400 more than I paid, so the repair option has to be considered by those that are aware!!
Satisfied reader!!
Quote >
Show me more. (place your curser over the diagram to enlarge
Use BACK to return to this page.
Having had the new unit fitted I now have an old but repairable unit that I can photograph and strip to show the component parts.
For comparison of the size of the components on this PCB the hole marked 1 is 5mm
The larger photo right hand side, is the actual size give or take a few mm.
What a pity the whole PCB, along with it's hundreds of components, precision plastic/metal bonded mouldings and other components become redundant just because of one small glass reeds fails.
The ECM portion of the unit above does look like rocket science
The MAFS is a component connected to the Engine control Module, printed circuit board.(ECM/PCB)and is then simply sited in a air intake manifold that connects directly to the air filter housing.
Having now removed the sensor from its chamber and removed the deflector/air foil (cover) the cause of the failure on my unit can be easily seen.
The reed/film marked 1 is in tacked.
The reed/film marked 2 although still in position is burnt, it is very obvious that this was the cause of the failure of this unit, and also why the car still ran so well. Neither of the reeds/films has completely broken or disappeared into the engine as I understand is more often the case; in such circumstances it is unlikely that the car would run and even if it did start is unlikely to be drivable.
A Shows the fine glass reads located between two metal posts , in each case these should be clean, unbroken or burnt. B Shows the plastic cowling that forms an 'air tunnel' around the reeds.
Despite the fine grill like structure over the sensor, without an purpose made air filter correctly installed the sensor would quickly become damaged.
Having now seen the fragile nature of the MAFS there is no way I would attempt to change/convert the 'air filter system' on my car, even the smallest particles of contamination or oil, finding their way onto sensor reed situated within the manifold/chamber could in my opinion damage the fine glass reeds that make up the Mass air sensing unit.
The grill seen in the above photo can be removed , this will enable you to see the MAFS much clearer but take car not to touch the reeds/film
I used two fine flat bladed screw drivers and gently teased the sleeve out, take note of its position or mark before removal
To replace simply press back in as found, grill nearest to the MAFS.
I future before fitting I will even put the air line over the new air filter to ensure there are no loose particles, even the smallest piece of debris or paper dust from the filter would I'm sure damage the fine glass reed as it heats up.
Cleaning the Reeds
If all you intend doing is cleaning your MAFS then you need go no further, the carburettor cleaner can be spraying into the throat of the ECU which will coat & clean the reeds, you may have to repeat this process several times but under no circumstances touch the reeds or you will break them off the metal supports one broken the car will not run. I strongly advise owners not to strip the ECU/MAFS down unless it is scrap as was the one I used on this page.
At the time mine went defective there were no companies repairing the units and so I was forced to pay close to £1000 for a new unit. I have since had it repaired and it is now usable should it be required But of course it will only work on my own car as mentioned it is coded by mercedes In Germany.
The Vehicle Wiring Harness is connected to the ECM/MAFS via the upper socket situated at the rear of the of the ECM/MAFS. 9 The lower socket allows connection of the Engine Wiring Harness 10 Although the official information says that these plugs are secured I could find no form of fixing on my car.
The ECM/MAFS is secured to the Air Filter housing at these three points. A
Note the sealing ring 7 which comes pre fitted on a new unit .
Note also that items 11 & 12 come pre fitted on a new unit and appears to be pre-fixed.
Seeing the components on the car makes life easier, to remove item 1 ease the top edge down and out it is held by a small lip on the top and bottom edge of the scoop.
This will then allow you to move item 2 back from the cross member , remove it from the air box housing by turning and pulling. When the resonator 5 is unscrewed the ECM/MAFS will be exposed.
Wayne a fellow owner has pointed out that the air intake hose in the photo above has in fact been put back incorrectly . Although it will fit and has no bearing on the air intake it does fit better when installed correctly. If your replacement ECU/MAFS has/is being fitted by professionals you might like to check your installation as well.
When fully assembled the mass Air sensor manifold is hidden by the resonator/cover, secured by three screws. The air induction hose is fitted to the air vent on the front cross member. Air is induced into the air access through plastic pipe work connected to the air filter housing then through the air filter and on through the grill in the induction manifold throat and on to the air sensor. Never be tempted to run your car without a purpose made air filter correctly installed.(See page. 16. for more details)
A quick look round one of the new 'A' class models revealed what appears to be a ECM on it's own situated on the right hand side of the bulk head but no sign of a mass air sensor in the form fitted to the facelift 'A160' 2/2001.
Although
looking through my own site I see there is what looks very much like a ECM sitting on the top of the engine in the new A150. So have Mercedes-Benz realised their mistake or not? Be assured if there is a next time with my car, the unit will be repaired.
It is worth remembering that if your car suffers a similar fate the mass air sensor can be repaired for £220 28/09 with a two year warrantee by a company
This information came to light after I had ordered the new ECM for my car. Ironically the new ECM from Mercedes-Benz had only got a 1 year warrantee. However be aware they do not repair the ECU portion of the combined unit.
Readers may be interested to read the comments of one of my readers who used this company who come highly recommended,
Quote Mass Airflow sensor - £250 + Vat, repaired thanks to Lofty's website and the mention of http://www.bba-reman.com, a company in Kent who repair MAFS not just for Mercedes cars. Great customer service, drove to Kent to deliver the part on Monday, contacted by 2pm on Tuesday to say it was fixed, delivered repaired on Wednesday before 12pm. Will highly recommend. Normally costs Upwards of £600 + vat ( this price is now grossly out of Date) Unquote
Quote Hi Lofty? Just thought it only right to let you know that I came across your website when researching alternative methods of repairs to my air flow meter which failed after 65000 miles on my 6 year old car. I received quotes of between £900 plus from my regular service agent (who assured me he would be cheaper than the official Mercedes dealer) and £550 plus VAT from a reputable local garage, who were going to send the unit away for rebuild.
In fact I followed your advice and had the rebuild done by BBA-Reman at a cost of £270+VAT and £8.50 postage.
The most remarkable thing was that I telephoned them on Thursday morning (mentioning your name), posted the unit to them Thursday afternoon, got a call from them Friday mid-day to confirm the fault & cost of repair....I received the repaired back at my home in Derbyshire at 9.00 am the FOLLOWING MONDAY !!!
Such excellent service is almost unprecedented in this day and age.
My only slight regret now is that I paid my local garage £50 to unplug the unit & replace it. I should have taken your advice and done it myself.
Thanks very much for the information which you took the trouble to post on the internet. It was very public spirited of you to do so. It's such a pity that having paid Mercedes £13K for the car new, they then have to rip off their clients on parts and service charges.
Thanks again! Ron Unquote
Please note the current price for the repair of your MAFS is £220.00 17/04/09
Mass Air sensors/Mass Air flow.( MAS/MAF) sensors.
Here's how they work. A constant voltage is applied to the heated reed or film. This film is positioned in the air stream or in an air flow sampling channel and is heated by the electrical current that the voltage produces. As air flows across it, it cools down. The heated reed/film is a positive temperature coefficient (pitch) resistor. This means that it's resistance drops when it's temperature drops. The drop in resistance allows more current to flow through it in order to maintain the programmed temperature. This current is changed to a frequency or a voltage which is sent to the computer and interpreted as air flow. Adjustments for air temperature and humidity are taken into consideration since they also affect the temperature of the heated wire or film.
Reinstalling the ECU/MAFS following repair.
Having had you MAFS repaired and re-set obviously it needs to be replaced. This is a very easy job and no skill is required with minimum tools, Do not let MB confuse you by saying the ECU needs to be set up to the car , this is not the case as it's the original ECU and still retains the settings. However having fitted and reconnected the battery , Turn on the ignition and let the car stand for a minute or so, this will allow the ECU to re-establish contact with all the various components on the car.
This action on your part also makes it less likely that the Engine management light will remain lit.
Should that be the case you will need to contact a Garage with a diagnostics tool to delete the light, NO other work is required by the garage. If you have your own diagnostics tool then simply delete the light.
Allow the car a couple of days to settle down after re-installing the repaired ECU/MAFS unit.
re-coding is not necessary as the unit is being re-fitted to the same car, It is understood from that when the repaired unit is re-fitted the ECM light should be automatically cancelled. But please read the information above and also please remember when re-fitting the car's battery to turn the lighting switch to at least side lights, remembering to turn them back OFF after reconnecting.
However If your car is pre 2000 it may well be that only a garage with 'Star' Diagnostics equipment can clear the fault from the ECU memory. Even if the light does extinguish the fault code for the defective ECM will stay logged until it is cleared It will have no effect on the running of the car. just one final point the time taken to turn your repaired unit round by BBA Reman and ECU testing is 3 to 4 days, it takes seven days for Mercedes-Bens parts to obtain your New combined ECM as it has to be coded to your car before delivery, so there is no advantage in buying a new unit, unless of course the ECM portion of the combined ECM/MAFS unit is defective.
The connector for the Diagnostics test equipment is located next to the bonnet release in the cabin, under the front edge of the shelf beneath the steering wheel.
My Final bill
, to put my car right was £950.00
that does not include the cost of the new oxygen sensor fitted which is being paid for by Mercedes-Benz
Some are WIS and some are otherwise I will certainly have any future MAFS defects repaired.
Today 18.04.09 the same job done by mercedes-Benz would cost nearer £1400.00
So what is the function of the oxygen sensors "Quote from NTK oxygen sensors. NTK is the brand name for oxygen sensors manufactured by NGK Spark Plugs. NGK is the world's largest manufacturer of oxygen sensors with over 10 million sensors produced annually.
Oxygen sensors are used in modern automobiles to control the fuel and ignition systems to optimise a car's performance in the areas of emissions and fuel economy. Sensors are located before and after the catalytic converter to check on the amount of oxygen in the exhaust. The sensor sends signals to the car's on-board computer, which then can adjust several variables, including air/fuel ratio and timing, in order to bring the engine into the optimum operating range Unquote
Link to yet more information, SVC,MAFS maintenance/cleaning
Read diagnostic reports:-
'Mobilo-life' report verbal only. (Oxygen sensor nearest to the engine.)
1st printed Diagnostic readout following Breakdown 24.10.05
2nd diagnostic test 2 11 05 following installation of oxygen sensor
Final diagnostic test after fitting new ECM/MAS.
UPDATE
As time goes on more information is coming available on the combined unit, one owner has recently suffered stalling of his engine erratic revs and general poor performance he also said he could hear the butterfly in the throttle control body flapping in an erratic matter . After many tests he got his car to an auto technician who diagnosed a breakdown of one of the electrical components within the ECU portion of the combined module, the fault code located was P0605
the out come was that he had to purchase and fit a new ECU from Mercedes-Benz this had to be coded to his car by MB in Germany before delivery and cost him just on a £1000. fitted. If you suffer problems on your ECU/MAFS DONT be tempted to go to a breakers yard, or E-bay where a number have be up for auction lately, like the ignition keys you will not be able to get the second hand unit re-coded and will therefore have wasted your money. Oh yes scrap yards and E bay sellers will sell them to you claiming they will work. They will not.
This is a question I put to one such seller on e-bay 30th May 2008 and the answer he gave in response-
MY question to the seller :-Q: The ECU /MAFS does as you say cost mega bucks, from MB that's because they are coded to the car, unless your unit is something very special yours will not work on anything other than the A class is came from.
Your in the salvage business you should be aware of that before you sell something to some unsuspecting buyer. http://aclassinfo.co.uk/mypage.38.htm 30-May-08
His reply:- A: We sell a lot of stuff like this to companies which refurbish /Reman them, this item is sold as is for spares or for someone to get it coded to their vehicle as a replacement, but thanks for the info anyway.
At least this seller was prepared to answer the question , a number of them don't.
However the answer given is not appropriate to the average buyer, parts may be salvageable by an expert, neither BBA Reman or ECU testing will repair the ECU portion of this unit .
as far as the buyer getting the unit re-coded this is not possible through normal means and I'm not aware of any organisation or company that will undertake this task. The same applies to ignition keys.
Another example
One thing that has been highlighted by the experience of this site and information is the array of faults that can be attributed to the defective mars, everything from the car not running at all to just high revs, erratic revs, on star-up, I think this next e-mail makes the point at just how obscure these defects can be:-
'Quote' ' This has just started in the last couple of weeks.
On a cold engine, the revs are steady for a few secs, then die right down, then surge back up, and then repeating. After a few minutes on the drive all is OK
. If I drive whilst it's still surging I get the kangaroo juice effect of the engine dieing and surging. Within a mile, or a couple of mins it's all settled down.
Car has done 89,000 miles and is due a one spanner service in 700 miles.
Any tips please, so I can point the garage in the right direction?
Following the A service on this car by MB, the plugs, ignition module, and oxygen sensors was replaced the car ran still ran the same, causing the owner some concern. Even a test of the 'Star' diagnostics tool failed to pick up the problem, and it's worth noting that Geoff did not have his engine management light in the instrument cluster lit as I had experienced, making the diagnoses of the fault even more difficult.
I suggested to him that the problem might be the Air mass sensor and he duly sent it off to www.ecutesting.com. who tested the unit and repaired it to him within hours of receipt
Geoff the owner of the car was delighted with the result:- quote:-
Refurbished unit, from ECU Testing of Nottingham, arrived 7:35am Saturday, as promised. Took about 10 minutes to fit and reset the windows. I'm very happy to say that the car is now back to normal! Total Cost = £265.91 inc return postage and Lofty's discount!
Great another happy MB owner.
So you can see from that experience that problems with your MAFS aren't quite such a disaster as they first appear, providing you do not go down the MB route.
One thing that is worth bearing in mind, both of the above companies will test your ECU/MAFS before attempting repair, if it is found not to be defective both companies will only charge a handling fee plus of course carriage, that works out only a few pounds more that a short diagnostics test with MB, and as with Geoff's car the fault may no show, money down the drain!!.
My Car is using more fuel now the ECU/MAFS has been repaired WHY?
One point that should be born in mind by all owners with MAFS problems, generally owners will complain of the car being sluggish and having no pulling/acceleration power. This is invariably caused by the lean mixture which is being provided to the engine controlled by the MAFS /ECU . IN this instance although the car is sluggish fuel consumption my be reasonable albeit a lean mixture providing more miles per gallon will eventually cause the valves of the engine to burn. It is therefore wise to get the MAFS sorted as soon a you realise there is a problem, remember you cannot always really on the Engine management light showing where the MMAFS is providing the lean mixture to the engine but the car will not run well and power is usually reduced or car stalls etc.
There have been a couple of instances of which I'm aware where the owners have noticed an increase in fuel consumption after having had the MAFS repaired, this will however be accompanied by increased performance in the engine and it's running should be back to the condition when the car was New.
If you experience this phenomenon and are not happy with t he amount of fuel used relative to miles driven, then there are several options:- 1. Run the car for a tank or two and then remove one of the plugs, if the plug is sooted up the mixture is rich.(too much fuel is being provided to the engine)
2. When the engine is warm, get a third party to cup a white cloth over the tail pipe of the exhaust for a minute or so, increase and decrease the revs over that period, apart from a few black smuts the exhaust gases should be free of soot.
3. Take your car to any MOT test station and ask them to do a gas analysis, if the car is running rich the readouts should indicate this.
If you are still unhappy contact the company who repaired your MAFS pointing out the problem they will be able to test your ECU/MAFS for you and confirm that the settings are correct or reset them for you, However of the dozens of ECU/MAFS I aware of that have been repaired I have only heard of complaints from two owners, so it is not a common problem.
Quote
Hi there Bert,
Again it should be remembered that there are other sensors in the exhaust gas system namely the lambda sensors fitted into the catalytic converter, some 'A@ Class have two sensors while others only have one I suspect it's the later models with the two sensors.
If having had your ECU?MAFS repaired /calibrated ,and still have the engine management light on then it may well be that one or both of the sensors need replacing.
This up until this week was another £300+ outlay however tony purchased his replacement units from a company and simply replaced the Bosch connector from the old units , that solved his problem for less the a third of the cost of mercedes Parts. see page 34.For more details We can re-test P's MAF on our flow bench if he wants to send it back in, we can compare his MAF readings against a new unit that we use as a reference. I have not known it before but If we have set his MAF incorrectly then we can easily rectify this on the bench. We have also had reports of higher fuel consumption from a couple of customers in the past but when we have tested the MAF voltage it has been perfect and when tested on the gas analyser it has been fine - I am not sure if it is the odd customer that is used to driving with a low voltage MAFS that causes sluggish performance but fantastic fuel consumption as it makes then engine run very weak, but then after having the MAF rebuilt they have all there power back and tend to use more fuel due to the extra power under there right foot.
We have tried to lower the MAF voltage slightly on one customers MAF before on request in an attempt to improve the fuel consumption but it just makes the engine sluggish again.
Kind regards
Unquote
I feel sure this mail clears up any doubts you may have about this matter.
The only time I would consider using a second hand ECU/MAFS is if I'm forced to buy a second hand /used engine in that case there are advantages to also obtaining and fitting the ECU/MAFS complete with throttle body from that car to yours, as this ensures the ECU/MAFS and electrical sensors on the engine newly fitted to your car compatible.
However you might like Maxine & Chris in Ireland, find that after having had a used replacement engine fitted the car will run rough for a while and then settle down, albeit they did obtain the two components mentioned with the used engine but did not fit them as the car seemed to run well, it later went through a rough patch but then settled down to run well. This is obviously due to the existing ECU/MAFS adjusting to meet the needs of the car & driver as MB claim happens, that the vehicle adjusts to the driving style etc.
Be aware the that there are more and more sellers on E-Bay trying to sell ECU/MAFS from 'A' Class cars and making all sorts of claims, they will not work on your car no matter how much , or little you pay
New buyers of USED 'A' Class cars .Seeing the amount of information on this document I would recommend to any new buyer of an 'A' Class to ask for a Full diagnostic printout on the prospective car. It will confirm that there are no outstanding faults, also ask for stored faults to be cleared from the ECM before delivery Some MB outlets will kick & struggle but insist or walk away.
My defective unit has now been repaired by BBA-Reman
Having retained my original but defective ECU/MAFS following it's replacement with a new unit some 18 months ago, I decided that as these units appear so vulnerable to defects, and as the price for New as well as Repairs is ever increasing I would get the old unit repaired, that way I would get it done before the price increased further and would then have a spare unit and as it was the original unit supplied with the car by Mercedes-Benz it would be ready coded, should I ever need it. failing that I could always sell it with the car. A Shows the plastic tunnel B are the two reeds that have been replaced.
Having made the decision
*I contacted BBA-Reman by phone,0930 on the 24th of July they arranged carriage and it was picked up within an hour & a half of my call by a courier.
* On the 25th I received a phone from BBA-Reman confirming it was defective and was repairable,
* Having given them the go ahead and made the payment by credit card, I was told it will be back with you tomorrow, sure enough the repaired unit was back early AM on the 26th just 48 hours inclusive of pick-up and repair.
The saving made against buying a New unit From Mercedes Benz was approx £550 at today's prices, which are of course ever increasing and the time saved in waiting for a New unit to be supplied and coded in Germany unit was at least 10-14 days providing Mercedes- have not got back orders to clear, which has happened in the past. One owner I am aware of waited 6 weeks for the unit to be ordered, delivered, and fitted. BBA-Reman even arranged the transport of the unit both collection and return, which avoids the need for you to look for a suitable courier and waste you time making phone calls. Do remember which ever company you use, not all units are repairable, in this case they will phone and inform you and only make a nominal handling charge + of course the carriage.
Let me explain what you are looking at in the above photo.
It is my original unit repaired, you can see one of the seals attached to the ECU, these must not be broken or you will invalidate your two year warrantee.
To obtain this photo I have merely removed the sleeve from the air inlet.
The large tunnel shaped feature is the plastic hood which goes over the two fine glass reeds, forming a wind tunnel, which directs the air entering the system via the Air Filter across the reeds, the two smaller tunnels are formed by to sets on metal legs one behind the other to which are attached the glass reeds, .
The combined assembly forms the air mass sensor along with of course the electronics shown on the PCB (printed circuit board) above, which determines the fuel/air mixture that you engine receives, both reeds must be in-tacked and not car boned up which is likely to occur if you do not use the standard dry air filter as supplied and fitted by Mercedes.
If you have problems and believe your MAFS is the cause of an engine running problem and are tempted to follow the cleaning procedure outlined on the SVC global site then stick to the procedure to the letter
DO NOT use compressed air in the area of these reeds and DO NOT TOUCH the reeds, they are extremely fragile and cannot be repaired by you the owner.
A word of Warning 17/06/09
If you have had your MAFS repaired by BBA Reman in recent years you need to check to see if the small 1/16" hole drilled in the top, back edge of the casing has been sealed. The need to drill this hole forms part of the BBA repair procedure However it does leave the ECU exposed to possible water damage if the hole has not been sealed, this should in my opinion be done with something like 'blue-tack', which can be removed if access to the hole is necessary at a later date.('DO NOT USE A NON REMOVABLE SEALANT') Having been alerted to the feature by an owner whose ECU failed following driving through a very severe storm, I inspected my own repaired ECU (spare unit) which has been in a box since repair,just two years ago, I was unaware of this hole or it's purpose until this week.
Had I fitted the ECU it could possibly have been exposed to elements not compatible which delicate electronics the likes of which are installed in the ECU/MAFS monolith. The drilling of this hole without it being re-sealed in my opinion negates the very good seals built into and integral of the unit casing.Not also the two wire 'u' shaped clips located by the ECU connections must be in place if the ECU is to remain water tight.
Cleaning your engine Bay
You are advised not to steam clean or wash under the bonnet with water/steam cleaning appliances, Both the ECU/MAFS along with the power steering pump and ESP/ABS systems are fitted with masses of sensitive electrical components many of which could be affected by such action.
Where possible avoid driving through water more the 10"-12" deep or the power steering pump electronics will become submerged and almost certainly fail, costing many hundreds of £££ to put right.
Repairs procedures followed by ECU Testing.com does not require the casing of the ECU to be drilled.
Return to Servicing
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* October 24th 2005. 'Mobilo-life' called due to stalling and rough running ECM (Engine Control Module) (Hand book ref.= Engine diagnosis Indicator lamp) was lit.
'Mobilo-life's' diagnostic's detected a defective oxygen sensor, located in the catalytic converter,
History
*Engine running normally, stalls on approach to roundabout,
* rolling re-start no problem, engine sounds rough,
* No dash warning lights at this point.
* Stopped for twenty minutes engine re-starts no problem,
* 500 yards engine sounds rough, acceleration erratic
* Engine Control Module lamp illuminates on dash display.
*Engine sounds as if is misfiring,* black smoke omitting from exhaust thereby giving an indication that the fuel to mixture ratio is incorrect. * Engine continued to run and I made it home 1.5 miles away.
Initial diagnosed Cause
There are two oxygen sensors both of similar appearance the one nearest the engine
1
is the one which the 'Mobilo-life' technician diagnostic equipment says has failed.The car was booked into an Independent Mercedes-Benz specialist www.mercedesj-a-haynes and I got an appointment for the repair to be carried out 4 days later during which time I did not use the car, However when the appointed garage tried to order the part, only the sensor at the back of catalytic converter was available. 2 The other is only available on a special order from Mercedes-Benz and the reason why it is required has to be specified along with chassis number etc, as it is not normal for it need replacement!
Action the garage therefore purchased the sensor available, (the sensor at the back of the cat. 2 Part Number A 002 540 01 17 (cost £149.69 inc (26/10/05
Availability of 02 sensors at greatly reduced prices.
For supply of replacement 02 sensors Lambda Sensors see page 34 09/06/09
this information was kindly provided by Tony, a fellow owner.
I digressed for good reason at that point because Mercedes Are now charging well over £150 per sensor.
However When I got the car out of my garage on the appointed day it started as normal and ran fine, although the engine management light was still displayed.
I arrived and left the car for the garage to fit the oxygen sensor and clear the fault, however when I returned I was told they had discovered further but related reasons as to why the ECM light was lit. a second diagnostic test had revealed that the mass air flow sensor had gone defective.
However if you have what appears to be a MAF Sensor problem Check that the air filter has been installed correctly and that the filter has been fully housed with filter lock fully slid into position this can cause the same symptoms as a MAFS defect as the air coming in the filter housing by passes the filter and flow direct to the MAF sensor.
These components ECM ( engine control module A and MAFS ( mass air flow sensor) B are integrated on the 'A' Class and therefore a fault developing one ,required them both to be replaced, at considerable cost, £764.05 plus VAT making a total bill of £897.76, a lot of anybodies money and I'm not amused.
I paid the garage for their time, diagnostic test and the part they had purchased on my behalf, they not being able to return it to MB Brighton, and in view of the fact that the car was still running normally drove it to my usual MB Garage, Main Dealer, who seeing the diagnostic sheet from the Independent Mercedes-Specialist confirmed that the fault was the Mass Air Flow Sensor.( MAFS) I had little choice but to order a ECM/MAFS combined unit which was going to take about 5 days to arrive, it being coded to my car at the factory
Having received this confirmed diagnoses I got the MB Garage to contact MB and ask them for a goodwill payment towards this cost, I received a direct refusal on parts and labour.
Having now driven some 50 + miles without a problem, apart from the ECM light showing on the dash display I still wasn't confident that the information I was being given was correct, and as I'd had to pay for the oxygen sensor I decided to fit it.
I then attended my local garage, the owner of whom I've known for years, he did an omissions test for me and the car was fine and would easily have passed an MOT. I then went back to the Specialist Mercedes Garage and asked them to delete the fault and then road test, sure enough the ECM light re-appeared after about few minutes of driving. That confirmed conclusively that it wasn't the sensor but that the fault was positively in the ECM/MAF. sensor.
This photo shows the crankcase breather pipe 1 interconnected with the pipe work of the ECU/MAFS, 2 this can be found full of oil/water brown emulsion, as shown below, and is best cleaned out before an oil change if, and when the need arises.
This small sample
3 is typical of the oil/water brown emulsion that can be found in the neck of the oil filler and also the crankcase breather pipe, more often than not caused by too many short runs where the engine is not able to reach its full operating temperature. Where this is a particular problem it is advisable to use engine flush prior to replacing the engine oil. The example in this photograph is nothing to worry about, although it was causing the owner some concern. I have seen much worse, a good long run and an oil change will normally deal with the problem.In any circumstances if the oil is changed at the prescribed intervals , not more than twelve months there will be no problem,
Do not confuse this problem with a leaking head gasket unless you are having to regularly top up the coolant header tank with fluid.
It was interesting to see the difference in the old and the new sensors , why the change in design I don't know I just hope it is for the good of the car and that Mercedes-Benz aren't using the 'A' Class as a test bed!I now contacted Mercedes Customer Services myself and explained the full scenario along with faxing them paperwork to substantiate that the wrong diagnoses/fault had been made and what it had cost me, as a result of my phone call Mercedes-Benz are going to reimburse me the £150.00 cost of the oxygen sensor.
Today 3 11 05 I have had the New ECM/MAFS fitted and asked for a diagnostic report showing that the New ECM/MAFS is fully functional and that the are no faults on the car at all.
I cant say that the car runs any different, a little smoother perhaps. But of course the ECM fault lamp has been extinguished, in truth I think the car is quieter running obviously due to the fuel/air mixture.
It is said that as you get older you get wiser! Well in this case it is true, since spending a great deal of money on my own car I have researched and am able to recommend two companies that will reliably repair the MAFS portion of the ECU/MAFS integrated unit fitted to the 'A' class, and ECU testing will undertake repairs to the ECU portion as well Great news as previously this has required a £1300 replacement unit from Mercedes-Benz, Germany, in both cases the companies place a two year warrantee on their repairs which is at least as long as Mercedes Benz New components.
Now I'm not only sharing this information with you but have arranged discounts with both companies so I hope the failure of your MAFS or now the ECU is not so traumatic and costly as mine .
Please do not confuse either of the companies below with this seller ashley1987-2008( 22) who is now advertising on E-Bay. I have no knowledge of the seller, and no discounts have been arranged. also note the repair is only guaranteed for a period of one year.
Remember if you choose to use one of the companies below for your repair, you will get a 15% discount if you mention my site 'Lofty's Homepage' or 'aclassinfo.co.uk' when placing your order, ,it will not be given automatically, other owners do not get this discount it is a perk arranged by lofty and very generously allowed by the companies mentioned to my readers in the case of both companies they offer a quick turn around and return of your repaired unit.
BBA Reman.co, location Rochester Kent. Telephone 0044-(0)1634-687222
The cost, £220 + carriage + Vat
Test only £35.00 + carriage + VAT.
Repairs undertaken by this Company are guaranteed for two years.
Please see my notes at the bottom of this page before making a decision as to which Company to use for the repair of your ECU/MAFS.
ECU Testing.com, Location, Derbyshire.Tel.0044(0)1773535638 or 07971468585
Business hours 9am to 6pm Monday to Friday, Location Derbyshire. will test and repair the MAFS integral of the ECU Cost £220
Please note THEY WILL ALSO UNDERTAKE REPAIRS TO THE ECU So if your in doubt as to whether your problem/fault is caused by either the MAFS or the ECU portion of your unit I would advise you to send it to them, they will be able to repair which ever is found to be faulty, if on test they find a repair is not required/necessary they will only charge £35.00 for handling, if you prefer to telephone, have the details of your ECU/MAFS to hand
Repairs undertaken by this Company are guaranteed for two years.
Hi there Lofty,
Just dropping you a line to say well done on the website, whenever we get anyone asking us how to remove there Mercedes A Class ECU/MAF we always direct them to your website. Every customer that reads it has commented how good your descriptions are and we are giving a lot of customers there 15% discount for mentioning your site.
There should be more sites like yours and you well deserve to do very well with it.
Kind regards
Roger & everyone at www.ecutesting.com
So there you have it, not only do they keep to their word and do a good job , they also appreciate your business and show it.
Hi Lofty, Just want to say thanks for all the info on your site. I had trouble with my MAFS so sent it off to ECU Testing. Phoned them on Mon and sent MAFS on Mon afternoon, it was returned by Wed morning and only cost £265 which is better than £1400 that two garages wanted. Also got 15% discount for mentioning your site. So thank you again. Gary.
Unquote
lets hope more readers will take this route when you encounter problems with your MAFS with a 15% discount can't be bad I wishes I known about my site when mine went !! sadly it wasn't written
For owners living abroad, One of my readers has used this company for his rebuild, you won't get information on how to remove fit etc but you have that info on this site, he paid 300€ and is very happy with the repair. www.actronics.nl Discounting is not arranged with this company.
Owners please be aware, if your car goes defective with a MAFS problem and is taken to a Mercedes garage for repairs MB will fit a new unit without question they will not want you having it repaired even though the warrantee period is greater than their new unit, so be on your guard you are the customer, it's your car tell them what your want done and stick to your guns or pay Six (6) times more for the new unit, fitted, the latest cost of New Mercedes -Benz ECU/MAFS sensor, fitted was £1400
There is no doubt that this monolith of MAFS/ECU combined is a complex unit, if you intend having it repaired then it is best left alone , this does not prevent you inspecting the reeds as this can be done by carefully the sleeve from the induction tube of the unit, see below
The latest information 10/04/09 reference Mercedes Costs for replacement and Fitting to one owner was £1400 approx, that's £400 more than I paid, so the repair option has to be considered by those that are aware!!
Satisfied reader!!
Quote >
Show me more. (place your curser over the diagram to enlarge
Use BACK to return to this page.
Having had the new unit fitted I now have an old but repairable unit that I can photograph and strip to show the component parts.For comparison of the size of the components on this PCB the hole marked 1 is 5mm
The larger photo right hand side, is the actual size give or take a few mm.
What a pity the whole PCB, along with it's hundreds of components, precision plastic/metal bonded mouldings and other components become redundant just because of one small glass reeds fails.
The ECM portion of the unit above does look like rocket scienceThe MAFS is a component connected to the Engine control Module, printed circuit board.(ECM/PCB)and is then simply sited in a air intake manifold that connects directly to the air filter housing.
Having now removed the sensor from its chamber and removed the deflector/air foil (cover) the cause of the failure on my unit can be easily seen. The reed/film marked 1 is in tacked.
The reed/film marked 2 although still in position is burnt, it is very obvious that this was the cause of the failure of this unit, and also why the car still ran so well. Neither of the reeds/films has completely broken or disappeared into the engine as I understand is more often the case; in such circumstances it is unlikely that the car would run and even if it did start is unlikely to be drivable.
A Shows the fine glass reads located between two metal posts , in each case these should be clean, unbroken or burnt. B Shows the plastic cowling that forms an 'air tunnel' around the reeds.
Despite the fine grill like structure over the sensor, without an purpose made air filter correctly installed the sensor would quickly become damaged.Having now seen the fragile nature of the MAFS there is no way I would attempt to change/convert the 'air filter system' on my car, even the smallest particles of contamination or oil, finding their way onto sensor reed situated within the manifold/chamber could in my opinion damage the fine glass reeds that make up the Mass air sensing unit.
The grill seen in the above photo can be removed , this will enable you to see the MAFS much clearer but take car not to touch the reeds/film I used two fine flat bladed screw drivers and gently teased the sleeve out, take note of its position or mark before removal
To replace simply press back in as found, grill nearest to the MAFS.
I future before fitting I will even put the air line over the new air filter to ensure there are no loose particles, even the smallest piece of debris or paper dust from the filter would I'm sure damage the fine glass reed as it heats up. Cleaning the Reeds
If all you intend doing is cleaning your MAFS then you need go no further, the carburettor cleaner can be spraying into the throat of the ECU which will coat & clean the reeds, you may have to repeat this process several times but under no circumstances touch the reeds or you will break them off the metal supports one broken the car will not run. I strongly advise owners not to strip the ECU/MAFS down unless it is scrap as was the one I used on this page.
At the time mine went defective there were no companies repairing the units and so I was forced to pay close to £1000 for a new unit. I have since had it repaired and it is now usable should it be required But of course it will only work on my own car as mentioned it is coded by mercedes In Germany.
The Vehicle Wiring Harness is connected to the ECM/MAFS via the upper socket situated at the rear of the of the ECM/MAFS. 9 The lower socket allows connection of the Engine Wiring Harness 10 Although the official information says that these plugs are secured I could find no form of fixing on my car.
The ECM/MAFS is secured to the Air Filter housing at these three points. A
Note the sealing ring 7 which comes pre fitted on a new unit .
Note also that items 11 & 12 come pre fitted on a new unit and appears to be pre-fixed.
Seeing the components on the car makes life easier, to remove item 1 ease the top edge down and out it is held by a small lip on the top and bottom edge of the scoop.
This will then allow you to move item 2 back from the cross member , remove it from the air box housing by turning and pulling. When the resonator 5 is unscrewed the ECM/MAFS will be exposed.
Wayne a fellow owner has pointed out that the air intake hose in the photo above has in fact been put back incorrectly . Although it will fit and has no bearing on the air intake it does fit better when installed correctly. If your replacement ECU/MAFS has/is being fitted by professionals you might like to check your installation as well.
When fully assembled the mass Air sensor manifold is hidden by the resonator/cover, secured by three screws. The air induction hose is fitted to the air vent on the front cross member. Air is induced into the air access through plastic pipe work connected to the air filter housing then through the air filter and on through the grill in the induction manifold throat and on to the air sensor. Never be tempted to run your car without a purpose made air filter correctly installed.(See page. 16. for more details) A quick look round one of the new 'A' class models revealed what appears to be a ECM on it's own situated on the right hand side of the bulk head but no sign of a mass air sensor in the form fitted to the facelift 'A160' 2/2001.
Although
looking through my own site I see there is what looks very much like a ECM sitting on the top of the engine in the new A150. So have Mercedes-Benz realised their mistake or not? Be assured if there is a next time with my car, the unit will be repaired.It is worth remembering that if your car suffers a similar fate the mass air sensor can be repaired for £220 28/09 with a two year warrantee by a company
This information came to light after I had ordered the new ECM for my car. Ironically the new ECM from Mercedes-Benz had only got a 1 year warrantee. However be aware they do not repair the ECU portion of the combined unit.
Readers may be interested to read the comments of one of my readers who used this company who come highly recommended,
Quote Mass Airflow sensor - £250 + Vat, repaired thanks to Lofty's website and the mention of http://www.bba-reman.com, a company in Kent who repair MAFS not just for Mercedes cars. Great customer service, drove to Kent to deliver the part on Monday, contacted by 2pm on Tuesday to say it was fixed, delivered repaired on Wednesday before 12pm. Will highly recommend. Normally costs Upwards of £600 + vat ( this price is now grossly out of Date) Unquote
Quote Hi Lofty? Just thought it only right to let you know that I came across your website when researching alternative methods of repairs to my air flow meter which failed after 65000 miles on my 6 year old car. I received quotes of between £900 plus from my regular service agent (who assured me he would be cheaper than the official Mercedes dealer) and £550 plus VAT from a reputable local garage, who were going to send the unit away for rebuild.
In fact I followed your advice and had the rebuild done by BBA-Reman at a cost of £270+VAT and £8.50 postage.
The most remarkable thing was that I telephoned them on Thursday morning (mentioning your name), posted the unit to them Thursday afternoon, got a call from them Friday mid-day to confirm the fault & cost of repair....I received the repaired back at my home in Derbyshire at 9.00 am the FOLLOWING MONDAY !!!
Such excellent service is almost unprecedented in this day and age.
My only slight regret now is that I paid my local garage £50 to unplug the unit & replace it. I should have taken your advice and done it myself.
Thanks very much for the information which you took the trouble to post on the internet. It was very public spirited of you to do so. It's such a pity that having paid Mercedes £13K for the car new, they then have to rip off their clients on parts and service charges.
Thanks again! Ron Unquote
Please note the current price for the repair of your MAFS is £220.00 17/04/09
Mass Air sensors/Mass Air flow.( MAS/MAF) sensors.
Here's how they work. A constant voltage is applied to the heated reed or film. This film is positioned in the air stream or in an air flow sampling channel and is heated by the electrical current that the voltage produces. As air flows across it, it cools down. The heated reed/film is a positive temperature coefficient (pitch) resistor. This means that it's resistance drops when it's temperature drops. The drop in resistance allows more current to flow through it in order to maintain the programmed temperature. This current is changed to a frequency or a voltage which is sent to the computer and interpreted as air flow. Adjustments for air temperature and humidity are taken into consideration since they also affect the temperature of the heated wire or film.
Reinstalling the ECU/MAFS following repair.
Having had you MAFS repaired and re-set obviously it needs to be replaced. This is a very easy job and no skill is required with minimum tools, Do not let MB confuse you by saying the ECU needs to be set up to the car , this is not the case as it's the original ECU and still retains the settings. However having fitted and reconnected the battery , Turn on the ignition and let the car stand for a minute or so, this will allow the ECU to re-establish contact with all the various components on the car.
This action on your part also makes it less likely that the Engine management light will remain lit.
Should that be the case you will need to contact a Garage with a diagnostics tool to delete the light, NO other work is required by the garage. If you have your own diagnostics tool then simply delete the light.
Allow the car a couple of days to settle down after re-installing the repaired ECU/MAFS unit.
re-coding is not necessary as the unit is being re-fitted to the same car, It is understood from that when the repaired unit is re-fitted the ECM light should be automatically cancelled. But please read the information above and also please remember when re-fitting the car's battery to turn the lighting switch to at least side lights, remembering to turn them back OFF after reconnecting.
However If your car is pre 2000 it may well be that only a garage with 'Star' Diagnostics equipment can clear the fault from the ECU memory. Even if the light does extinguish the fault code for the defective ECM will stay logged until it is cleared It will have no effect on the running of the car. just one final point the time taken to turn your repaired unit round by BBA Reman and ECU testing is 3 to 4 days, it takes seven days for Mercedes-Bens parts to obtain your New combined ECM as it has to be coded to your car before delivery, so there is no advantage in buying a new unit, unless of course the ECM portion of the combined ECM/MAFS unit is defective.
The connector for the Diagnostics test equipment is located next to the bonnet release in the cabin, under the front edge of the shelf beneath the steering wheel.
My Final bill
, to put my car right was £950.00
that does not include the cost of the new oxygen sensor fitted which is being paid for by Mercedes-Benz
Some are WIS and some are otherwise I will certainly have any future MAFS defects repaired.
Today 18.04.09 the same job done by mercedes-Benz would cost nearer £1400.00
So what is the function of the oxygen sensors "Quote from NTK oxygen sensors. NTK is the brand name for oxygen sensors manufactured by NGK Spark Plugs. NGK is the world's largest manufacturer of oxygen sensors with over 10 million sensors produced annually.
Oxygen sensors are used in modern automobiles to control the fuel and ignition systems to optimise a car's performance in the areas of emissions and fuel economy. Sensors are located before and after the catalytic converter to check on the amount of oxygen in the exhaust. The sensor sends signals to the car's on-board computer, which then can adjust several variables, including air/fuel ratio and timing, in order to bring the engine into the optimum operating range Unquote
Link to yet more information, SVC,MAFS maintenance/cleaning
Read diagnostic reports:-
'Mobilo-life' report verbal only. (Oxygen sensor nearest to the engine.)
1st printed Diagnostic readout following Breakdown 24.10.05
2nd diagnostic test 2 11 05 following installation of oxygen sensor
Final diagnostic test after fitting new ECM/MAS.
UPDATE
As time goes on more information is coming available on the combined unit, one owner has recently suffered stalling of his engine erratic revs and general poor performance he also said he could hear the butterfly in the throttle control body flapping in an erratic matter . After many tests he got his car to an auto technician who diagnosed a breakdown of one of the electrical components within the ECU portion of the combined module, the fault code located was P0605
the out come was that he had to purchase and fit a new ECU from Mercedes-Benz this had to be coded to his car by MB in Germany before delivery and cost him just on a £1000. fitted. If you suffer problems on your ECU/MAFS DONT be tempted to go to a breakers yard, or E-bay where a number have be up for auction lately, like the ignition keys you will not be able to get the second hand unit re-coded and will therefore have wasted your money. Oh yes scrap yards and E bay sellers will sell them to you claiming they will work. They will not.
This is a question I put to one such seller on e-bay 30th May 2008 and the answer he gave in response-
MY question to the seller :-Q: The ECU /MAFS does as you say cost mega bucks, from MB that's because they are coded to the car, unless your unit is something very special yours will not work on anything other than the A class is came from.
Your in the salvage business you should be aware of that before you sell something to some unsuspecting buyer. http://aclassinfo.co.uk/mypage.38.htm 30-May-08
His reply:- A: We sell a lot of stuff like this to companies which refurbish /Reman them, this item is sold as is for spares or for someone to get it coded to their vehicle as a replacement, but thanks for the info anyway.
At least this seller was prepared to answer the question , a number of them don't.
However the answer given is not appropriate to the average buyer, parts may be salvageable by an expert, neither BBA Reman or ECU testing will repair the ECU portion of this unit .
as far as the buyer getting the unit re-coded this is not possible through normal means and I'm not aware of any organisation or company that will undertake this task. The same applies to ignition keys.
Another example
One thing that has been highlighted by the experience of this site and information is the array of faults that can be attributed to the defective mars, everything from the car not running at all to just high revs, erratic revs, on star-up, I think this next e-mail makes the point at just how obscure these defects can be:-
'Quote' ' This has just started in the last couple of weeks.
On a cold engine, the revs are steady for a few secs, then die right down, then surge back up, and then repeating. After a few minutes on the drive all is OK
. If I drive whilst it's still surging I get the kangaroo juice effect of the engine dieing and surging. Within a mile, or a couple of mins it's all settled down.
Car has done 89,000 miles and is due a one spanner service in 700 miles.
Any tips please, so I can point the garage in the right direction?
Following the A service on this car by MB, the plugs, ignition module, and oxygen sensors was replaced the car ran still ran the same, causing the owner some concern. Even a test of the 'Star' diagnostics tool failed to pick up the problem, and it's worth noting that Geoff did not have his engine management light in the instrument cluster lit as I had experienced, making the diagnoses of the fault even more difficult.
I suggested to him that the problem might be the Air mass sensor and he duly sent it off to www.ecutesting.com. who tested the unit and repaired it to him within hours of receipt
Geoff the owner of the car was delighted with the result:- quote:-
Refurbished unit, from ECU Testing of Nottingham, arrived 7:35am Saturday, as promised. Took about 10 minutes to fit and reset the windows. I'm very happy to say that the car is now back to normal! Total Cost = £265.91 inc return postage and Lofty's discount!
Great another happy MB owner.
So you can see from that experience that problems with your MAFS aren't quite such a disaster as they first appear, providing you do not go down the MB route.
One thing that is worth bearing in mind, both of the above companies will test your ECU/MAFS before attempting repair, if it is found not to be defective both companies will only charge a handling fee plus of course carriage, that works out only a few pounds more that a short diagnostics test with MB, and as with Geoff's car the fault may no show, money down the drain!!.
My Car is using more fuel now the ECU/MAFS has been repaired WHY?
One point that should be born in mind by all owners with MAFS problems, generally owners will complain of the car being sluggish and having no pulling/acceleration power. This is invariably caused by the lean mixture which is being provided to the engine controlled by the MAFS /ECU . IN this instance although the car is sluggish fuel consumption my be reasonable albeit a lean mixture providing more miles per gallon will eventually cause the valves of the engine to burn. It is therefore wise to get the MAFS sorted as soon a you realise there is a problem, remember you cannot always really on the Engine management light showing where the MMAFS is providing the lean mixture to the engine but the car will not run well and power is usually reduced or car stalls etc.
There have been a couple of instances of which I'm aware where the owners have noticed an increase in fuel consumption after having had the MAFS repaired, this will however be accompanied by increased performance in the engine and it's running should be back to the condition when the car was New.
If you experience this phenomenon and are not happy with t he amount of fuel used relative to miles driven, then there are several options:- 1. Run the car for a tank or two and then remove one of the plugs, if the plug is sooted up the mixture is rich.(too much fuel is being provided to the engine)
2. When the engine is warm, get a third party to cup a white cloth over the tail pipe of the exhaust for a minute or so, increase and decrease the revs over that period, apart from a few black smuts the exhaust gases should be free of soot.
3. Take your car to any MOT test station and ask them to do a gas analysis, if the car is running rich the readouts should indicate this.
If you are still unhappy contact the company who repaired your MAFS pointing out the problem they will be able to test your ECU/MAFS for you and confirm that the settings are correct or reset them for you, However of the dozens of ECU/MAFS I aware of that have been repaired I have only heard of complaints from two owners, so it is not a common problem.
Quote
Hi there Bert,
Again it should be remembered that there are other sensors in the exhaust gas system namely the lambda sensors fitted into the catalytic converter, some 'A@ Class have two sensors while others only have one I suspect it's the later models with the two sensors.
If having had your ECU?MAFS repaired /calibrated ,and still have the engine management light on then it may well be that one or both of the sensors need replacing.
This up until this week was another £300+ outlay however tony purchased his replacement units from a company and simply replaced the Bosch connector from the old units , that solved his problem for less the a third of the cost of mercedes Parts. see page 34.For more details We can re-test P's MAF on our flow bench if he wants to send it back in, we can compare his MAF readings against a new unit that we use as a reference. I have not known it before but If we have set his MAF incorrectly then we can easily rectify this on the bench. We have also had reports of higher fuel consumption from a couple of customers in the past but when we have tested the MAF voltage it has been perfect and when tested on the gas analyser it has been fine - I am not sure if it is the odd customer that is used to driving with a low voltage MAFS that causes sluggish performance but fantastic fuel consumption as it makes then engine run very weak, but then after having the MAF rebuilt they have all there power back and tend to use more fuel due to the extra power under there right foot.
We have tried to lower the MAF voltage slightly on one customers MAF before on request in an attempt to improve the fuel consumption but it just makes the engine sluggish again.
Kind regards
Unquote
I feel sure this mail clears up any doubts you may have about this matter.
The only time I would consider using a second hand ECU/MAFS is if I'm forced to buy a second hand /used engine in that case there are advantages to also obtaining and fitting the ECU/MAFS complete with throttle body from that car to yours, as this ensures the ECU/MAFS and electrical sensors on the engine newly fitted to your car compatible.
However you might like Maxine & Chris in Ireland, find that after having had a used replacement engine fitted the car will run rough for a while and then settle down, albeit they did obtain the two components mentioned with the used engine but did not fit them as the car seemed to run well, it later went through a rough patch but then settled down to run well. This is obviously due to the existing ECU/MAFS adjusting to meet the needs of the car & driver as MB claim happens, that the vehicle adjusts to the driving style etc.
Be aware the that there are more and more sellers on E-Bay trying to sell ECU/MAFS from 'A' Class cars and making all sorts of claims, they will not work on your car no matter how much , or little you pay
New buyers of USED 'A' Class cars .Seeing the amount of information on this document I would recommend to any new buyer of an 'A' Class to ask for a Full diagnostic printout on the prospective car. It will confirm that there are no outstanding faults, also ask for stored faults to be cleared from the ECM before delivery Some MB outlets will kick & struggle but insist or walk away.
My defective unit has now been repaired by BBA-Reman
Having retained my original but defective ECU/MAFS following it's replacement with a new unit some 18 months ago, I decided that as these units appear so vulnerable to defects, and as the price for New as well as Repairs is ever increasing I would get the old unit repaired, that way I would get it done before the price increased further and would then have a spare unit and as it was the original unit supplied with the car by Mercedes-Benz it would be ready coded, should I ever need it. failing that I could always sell it with the car. A Shows the plastic tunnel B are the two reeds that have been replaced.
Having made the decision
*I contacted BBA-Reman by phone,0930 on the 24th of July they arranged carriage and it was picked up within an hour & a half of my call by a courier.
* On the 25th I received a phone from BBA-Reman confirming it was defective and was repairable,
* Having given them the go ahead and made the payment by credit card, I was told it will be back with you tomorrow, sure enough the repaired unit was back early AM on the 26th just 48 hours inclusive of pick-up and repair.
The saving made against buying a New unit From Mercedes Benz was approx £550 at today's prices, which are of course ever increasing and the time saved in waiting for a New unit to be supplied and coded in Germany unit was at least 10-14 days providing Mercedes- have not got back orders to clear, which has happened in the past. One owner I am aware of waited 6 weeks for the unit to be ordered, delivered, and fitted. BBA-Reman even arranged the transport of the unit both collection and return, which avoids the need for you to look for a suitable courier and waste you time making phone calls. Do remember which ever company you use, not all units are repairable, in this case they will phone and inform you and only make a nominal handling charge + of course the carriage.
Let me explain what you are looking at in the above photo.
It is my original unit repaired, you can see one of the seals attached to the ECU, these must not be broken or you will invalidate your two year warrantee.
To obtain this photo I have merely removed the sleeve from the air inlet.
The large tunnel shaped feature is the plastic hood which goes over the two fine glass reeds, forming a wind tunnel, which directs the air entering the system via the Air Filter across the reeds, the two smaller tunnels are formed by to sets on metal legs one behind the other to which are attached the glass reeds, .
The combined assembly forms the air mass sensor along with of course the electronics shown on the PCB (printed circuit board) above, which determines the fuel/air mixture that you engine receives, both reeds must be in-tacked and not car boned up which is likely to occur if you do not use the standard dry air filter as supplied and fitted by Mercedes.
If you have problems and believe your MAFS is the cause of an engine running problem and are tempted to follow the cleaning procedure outlined on the SVC global site then stick to the procedure to the letter
DO NOT use compressed air in the area of these reeds and DO NOT TOUCH the reeds, they are extremely fragile and cannot be repaired by you the owner.
A word of Warning 17/06/09
If you have had your MAFS repaired by BBA Reman in recent years you need to check to see if the small 1/16" hole drilled in the top, back edge of the casing has been sealed. The need to drill this hole forms part of the BBA repair procedure However it does leave the ECU exposed to possible water damage if the hole has not been sealed, this should in my opinion be done with something like 'blue-tack', which can be removed if access to the hole is necessary at a later date.('DO NOT USE A NON REMOVABLE SEALANT') Having been alerted to the feature by an owner whose ECU failed following driving through a very severe storm, I inspected my own repaired ECU (spare unit) which has been in a box since repair,just two years ago, I was unaware of this hole or it's purpose until this week.
Had I fitted the ECU it could possibly have been exposed to elements not compatible which delicate electronics the likes of which are installed in the ECU/MAFS monolith. The drilling of this hole without it being re-sealed in my opinion negates the very good seals built into and integral of the unit casing.Not also the two wire 'u' shaped clips located by the ECU connections must be in place if the ECU is to remain water tight.
Cleaning your engine Bay
You are advised not to steam clean or wash under the bonnet with water/steam cleaning appliances, Both the ECU/MAFS along with the power steering pump and ESP/ABS systems are fitted with masses of sensitive electrical components many of which could be affected by such action.
Where possible avoid driving through water more the 10"-12" deep or the power steering pump electronics will become submerged and almost certainly fail, costing many hundreds of £££ to put right.
Repairs procedures followed by ECU Testing.com does not require the casing of the ECU to be drilled.
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