Merc 2003 Engine Fault light problem

toby83

Hi , I am new to this but have pulled out what hair i have left on this persistant problem! ( fuel mix is too rich co2 emmission / similar -causing fault light to come on )

I have replaced 3 breather hoses and a value in 12 months and still this problem persists. It was fine until I had it serviced in june 08 and immediatley the next day the fault re-appeared again.

The car was diagnosed again last week and guess what the merc diagnostic sw says its the breather hose.

I am an engineer and not a mechanic but I am sure the 4th breather hose will will not fix my problem.

I would appreciate any advise or has anyone come across this problem as I do not know where to go with this !.

toby83

Mr.Diagnostic

There is not much to go on from your post so this reply will be a bit on the general side.

If the fault occurred after the service then it could be related. Its not that I am trying to lay blame but it is likely to be connected to the service work. Something that was weak could have been disturbed etc. (you say “re-appeared” which confuses the issue somewhat). That is a route worth investigating.

Do you have any detail on the fault diagnosis or trouble codes? If you do post details along with details of what the car is. VIN would be a good idea as there were engine changes in 2003 (PM the vin if you like). Without more detail on trouble codes etc there is not much anyone could advise.

What you need is a good diagnostic or Mercedes specialist. If you post your location someone will probably be able to make a recommendation.

toby83

Hi Mr Diagnostic ,

Many thanks for the prompt response.

I have the fault codes at home and can send to you tomorrow - The vin number Ithink start with WDC 203xxxxxxxxx is this it ?

The car when submitted for a service in mid 07 had the fault condition intermittently for about 2 weeks but came on solid the week prior to the service date.(Car was hunting - term merc used to explain the sympton )

I showed the fault on the display to the merc dealer mechanic that morning who said it was the breather hose to the super charger without even putting the diagnostic tool on the car.The car was serviced , breather hose replaced and within 24hr the fault light came on again. I returned to dealer as the symptons were the same ( car slightly hunting ( rev counter dancing ) when at the ligths , but not enough to stall ).He said it was a different fault now and caused by a second breather hose !! hello !!

I decided to go to another merc dealer for second opinion who diagnosed the fault to be the same breather hose that was replaced during the service ? I said it couldn't be as that very hose was installed only 48 hr ago as a brand new part.He gave me the fault codes which I will send tomorrow as I do not have them here with me.He advised to go back to other merc dealer as he had not corrected the fault!

I went back to my own merc dealer again with a hard copy of these codes and he took the car for 4 days , replaced the second breather hose and a one way valve and mentioned about having to get a software file download and charged me another 600 euros.

The car was working but felt it wasn't 100% .Fuel efficiency wasn't as good , seemed slower to give me power when I wanted it.

I feel they hadn't found the problem but has done somthing else apart from replacing the hoses , to mask the problem via the software?

I returned for my next service last June/july 08 .The car just needed usual wear and tear items and had warranty upgrades to be done, battery , door seals .There were no other faults with the car!!

However two days after the service - the same fault light comes on again as last year.

I returned and inquired about the reoccurrance of the fault and if they had changed /upgraded the software as part of the service ?

In my view this was the only component that I could think off that may have upset the sensitivity of the car and possibly re trigger the fault.

They said they had not and all they offered was to look at the car again and give me a quote to fix it eventhough it did not have the fault before the service but now had it after the service . I have paid over 1200 euros alone on this one fault for 3 hoses in 12 mths !!. I said no thanks.

I have since had the car checked by a merc specialist who's used the same diagnostic tool as merc and identified to me that the breather hose that was replaced last june is the problem!! deja vue , but he would start with this breather hose as its the cheapest to fix , thereafter he would progress to 3 other associated parts in the circuit , an oxygen sensor , a three way value and sometihing else. Really he is not offering any better service than what merc had done to date.

Its like going to the dentist with a toothache and paying to have all your teeth out one by one until he is left with the problem tooth.

Merc specialist's answer ,to not being able to find the problem is that the merc software diagnostic tool is old , 1995 and out of date technology -

I will send the codes tomorrow.
Thanks again

toby83

Mr.Diagnostic

Hi,

Ok, so it’s a c class Kompressor. The breather pipe that everyone wants to change is a common issue but obviously not the cause in this case, or at least probably not the latest episode.
Yes, WDC203xxxxxxx is what I need along with the codes. I suspect I know what the codes will be anyway. Hopefully you got a printout and not just a list.

Very often fault codes can be set for more than one reason. The code that normally sets in this instance is due to the oxygen sensor signal being out of range. A vac leak from any source can cause this. It just happens that the hose in question is the most common cause on that engine. The trick with this code, or any code, is to check the “code setting criteria” and work from there. Fitting the part that usually causes this code is based on product knowledge. When product knowledge fails then best practice diagnostics have to take over. As far as I am concerned this involves testing to find and prove the fault rather than “bolt on diagnostics”.

The merc factory tool is totally up to date. It is not a simple tool to use to its full potential but it is one of the better factory tools. It has the ability to access a great depth of info on most fault codes rather than just the codes.

If your software was updated in mid 2007 its unlikely there is a newer version available. The factory tool will not allow flashing back to an earlier version so that will not be the issue.

Send me whatever details you have and I will comment further.

toby83

Hi ,

Many thanks again ,and you are correct , the software is only as good as the person who can interrogate it !

I have pulled the hardcopy that was given to me by the second merc dealer 48 hr after the first hose was replaced and car had been serviced in Oct 07 last , as follows:

Model 203.046Fault Codes Code Text Status 2029-001Selfadaption of mixture formation at rich stop ( tendancy of Current and engine towards lean stored 2029-002Selfadaption of mixture formation at lean stop (tendancy of Current and engine towards rich stored 200A-002B2/5 (Hot film mass air flow sensor ), short circuit to ground/☼Stored Open Circuit in wiring [P0102] 200A-004B2/5 (Hot film mass air flow sensor) , Plausibility error Mass☼Stored air flow sensor / Throttle valve / intake manifold pressure [P01001] 201C-002Selfadaption of mixture formation , The mixture is too lean in the Stored part load range.[ P0171]
This was the fault code printout prior to the second and third hose being installed - I would assume the same fault has now prompted the latest garage to change the same hose yet again, obviously a fruitless exercise and just more expense without the benefit.

By the way I am based in Dublin !

Hope this helps ?

thanks again its appreciated...

toby83

Mr.Diagnostic

Right, that gives a better idea of what is happening.
Your engine is the newer type. On the earlier type these fault codes were common but the diagnosis was, in general, a little different. I have cleaned up your code list below and Having gone through then a few things are noteworthy.
The first two codes contradict each other. The only time I have ever seen this happen was when an O2 sensor was left out for test purposes.
The third code could be genuine but is more likely to have been caused by someone disconnecting the MAF with the ignition on.

The fourth code is the telling one for me. It suggests an airflow/engine breathing
problem
On this engine this particular code is normally caused by one of two things. Either a dirty throttle body that has lost its adaption values in the ECU or a blocked cat. I have seen a few of these where a misfire has damaged the cat and the damaged/blocked cat is then mistaken for the cause. The cause is likely to ignition, MAF, or sticky valves.

I would bet the cat is blocked but that there is an underlying issue also. Cats are expensive so this would need to be confirmed first.

Aside from the code info that you posted it is also possible to read freeze frame data for each of those codes. This helps as it shows the status of various sensor signals when the code was set as well as how many times the code was set.

Really the first thing to do in a case like this is to clear the error memory, drive it, read it again and see what codes come back. Based on this an analysis of processed data from the ECU would get you somewhere closer to a result. It is possible that some of the codes were set due to the work that was done.


2029-001Selfadaption of mixture formation at rich stop (Current and stored tendancy of engine towards lean

2029-002Selfadaption of mixture formation at lean stop (Current and stored tendancy of engine towards rich

200A-002B2/5 (Hot film mass air flow sensor ), short circuit to ground/☼ Open Circuit in wiring Stored

[P0102]200A-004B2/5 (Hot film mass air flow sensor) , Plausibility error Mass☼ air flow sensor / Throttle valve / intake manifold pressure Stored

[P01001]201C-002Selfadaption of mixture formation , The mixture is too lean in the part load range.[ P0171] Stored

Darragh29

Suerly a Merc dealer would have cleared codes that were generated during diagnostic work before letting the car back out, especially with a case history like this???

These clump of codes look to me like they were generated by someone disconnecting sensors and trying to diagnose a problem in this way. I used to have a friend who had a garage and he wasn't into computers or computer diagnostics, he would always start disconnecting sensors to see if this had any impact on the problem. Eventually he would bring it down to me and I'd hook it up and the first thing I'd notice would be a load of DTC's sitting on the ECU that had been generated by him pr*cking around with disconnecting sensors and taking a hit and miss approach. Usually when I cleared these, I was left with one actual fault code that was relevant to the problem.

I agree with Mr.D, clear all these codes away and start on a clean sheet. The fuel trim fault codes look like the lambda sensor was disconnected at some stage.

toby83

Hi again ,

Ok then , the merc specialist who checked the car last friday and offered to replace the hose, but I declined , may have cleared the faults as the display does not currently show the fault.

However , it will over time trigger again , I am sure and seems to come on if I am sitting in traffic , idle , for a long while - well that's been my experience in the past few weeks, but I could be wrong and trying to hard to establsih the symptons to find the fault!

Anyway , when it does come on again , who /where would one find someone with your obvious diagnotic depth of knowledge and skill to address the problem- ?

I live in Dublin.

thanks again

toby83




=Mr.Diagnostic;57349063]Right, that gives a better idea of what is happening.
Your engine is the newer type. On the earlier type these fault codes were common but the diagnosis was, in general, a little different. I have cleaned up your code list below and Having gone through then a few things are noteworthy.
The first two codes contradict each other. The only time I have ever seen this happen was when an O2 sensor was left out for test purposes.
The third code could be genuine but is more likely to have been caused by someone disconnecting the MAF with the ignition on.

The fourth code is the telling one for me. It suggests an airflow/engine breathing
problem
On this engine this particular code is normally caused by one of two things. Either a dirty throttle body that has lost its adaption values in the ECU or a blocked cat. I have seen a few of these where a misfire has damaged the cat and the damaged/blocked cat is then mistaken for the cause. The cause is likely to ignition, MAF, or sticky valves.

I would bet the cat is blocked but that there is an underlying issue also. Cats are expensive so this would need to be confirmed first.

Aside from the code info that you posted it is also possible to read freeze frame data for each of those codes. This helps as it shows the status of various sensor signals when the code was set as well as how many times the code was set.

Really the first thing to do in a case like this is to clear the error memory, drive it, read it again and see what codes come back. Based on this an analysis of processed data from the ECU would get you somewhere closer to a result. It is possible that some of the codes were set due to the work that was done.


2029-001Selfadaption of mixture formation at rich stop (Current and stored tendancy of engine towards lean

2029-002Selfadaption of mixture formation at lean stop (Current and stored tendancy of engine towards rich

200A-002B2/5 (Hot film mass air flow sensor ), short circuit to ground/☼ Open Circuit in wiring Stored

[P0102]200A-004B2/5 (Hot film mass air flow sensor) , Plausibility error Mass☼ air flow sensor / Throttle valve / intake manifold pressure Stored

[P01001]201C-002Selfadaption of mixture formation , The mixture is too lean in the part load range.[ P0171] Stored[/quote]

toby83

Hello Darragh 29 ,

You would think so , but again as I said to Mr Diagnostic , you are only as good as your ability to interroagte and understand the diagnostic tools you are using.

I think Mr Diagnostic has a good understanding of the problem - and has identifed more in 48 hr than 3 main merc dealers and two specialists todate.

Anyway I will wait for the fault to reappear and then hopefully find someone who can utilise the tools as effectively as Mr Diagnostic !

Any suggestions ?

Thanks again ,

toby83

Darragh29 wrote: »

Suerly a Merc dealer would have cleared codes that were generated during diagnostic work before letting the car back out, especially with a case history like this???

These clump of codes look to me like they were generated by someone disconnecting sensors and trying to diagnose a problem in this way. I used to have a friend who had a garage and he wasn't into computers or computer diagnostics, he would always start disconnecting sensors to see if this had any impact on the problem. Eventually he would bring it down to me and I'd hook it up and the first thing I'd notice would be a load of DTC's sitting on the ECU that had been generated by him pr*cking around with disconnecting sensors and taking a hit and miss approach. Usually when I cleared these, I was left with one actual fault code that was relevant to the problem.

I agree with Mr.D, clear all these codes away and start on a clean sheet. The fuel trim fault codes look like the lambda sensor was disconnected at some stage.

VH

toby83 wrote: »

Anyway I will wait for the fault to reappear and then hopefully find someone who can utilise the tools as effectively as Mr Diagnostic !

Any suggestions ?

i think you answered the question yourself

Darragh29

toby83 wrote: »

Hello Darragh 29 ,

You would think so , but again as I said to Mr Diagnostic , you are only as good as your ability to interroagte and understand the diagnostic tools you are using.

I think Mr Diagnostic has a good understanding of the problem - and has identifed more in 48 hr than 3 main merc dealers and two specialists todate.

Anyway I will wait for the fault to reappear and then hopefully find someone who can utilise the tools as effectively as Mr Diagnostic !

Any suggestions ?

Thanks again ,

toby83

Well Mr D said this before on another thread but it's not so much the ability to use diagnostic tools as it is an ability to understand the fundamentals of what is happening at component level. Some of the engine signal problems you'll see these days on cars are something that an electronic engineer would be used to seeing than a mechanic.

toby83

Hi Darragh ,

I agree totally and really the diagnostic aids now on these cars as more complex and alien to the skills of the mechanic - However, when you consider the rates they charge today for such you would expect at least for the garage to have a somebody compentent enough to identify the root cause analysis using the software aid and thereafter instruct the mechanic to the appropriate repair action etc .Anybody , or an apprentice can keep replacing good parts time after time as eventaully they will hit on the smoking gun as they say !!but that's a cost I for one cannot afford.

I think the only thing for it with next car going forward is a service warranty contract .Then they can replace all the parts they want to their hearts content as I will only be paying for wear and tear ..

toby83

Darragh29 wrote: »

Well Mr D said this before on another thread but it's not so much the ability to use diagnostic tools as it is an ability to understand the fundamentals of what is happening at component level. Some of the engine signal problems you'll see these days on cars are something that an electronic engineer would be used to seeing than a mechanic.

Mr.Diagnostic

toby83 wrote: »

Anyway I will wait for the fault to reappear

Hi Toby,

Quick question for you. When the light is not on is the hunting idle or any other symptom still present?

As regards the light coming on some codes will cause the light and others will not. The light not being on does not mean there is no diagnostic trail to follow. The mixture adaption codes will cause a light but only when the adaption limit is reached. This can take a while to happen.

I will PM you my contact details.

HTH

Darsad

Hey Toby

Reading your post I had a very similar problem on an 02 e 200 Auto . I was pulling my hair out and had bought a new Air flow meter cleaned out everything etc etc but the MIl would come back on every so often.

Problem turned out to be a know merc issue in that the Auot box leaks
at the main round wiring loom and capilleries up the loom causing numerous different codes to reoccur not sure if yours is Auto but may be worth having a look at, the same thing can also happen to the front cam sensor so remove the block connector and check for oil contamanitaion

May Help

toby83

hi ,

As it turns out it is an 03 c180 auto and this was never brought to my attention so far , but really I am convinced they have no idea of how to diagnose any fault beyond the marco level of the very tools they have available to them.Maybe they just ring around between garages and if nobody has experienced a similar fault they just go with the recommendation posted against the fault code- and consdieirng they charge consultancy type rates its a very expensive situation such as these type of faults for the consumer.

thanks I will keep this in mind as I progress .

At the end of this I could open a freelance repair shop for mercs !!!

toby 83

Darsad wrote: »

Hey Toby

Reading your post I had a very similar problem on an 02 e 200 Auto . I was pulling my hair out and had bought a new Air flow meter cleaned out everything etc etc but the MIl would come back on every so often.

Problem turned out to be a know merc issue in that the Auot box leaks
at the main round wiring loom and capilleries up the loom causing numerous different codes to reoccur not sure if yours is Auto but may be worth having a look at, the same thing can also happen to the front cam sensor so remove the block connector and check for oil contamanitaion

May Help

Darragh29

toby83 wrote: »

hi ,

As it turns out it is an 03 c180 auto and this was never brought to my attention so far , but really I am convinced they have no idea of how to diagnose any fault beyond the marco level of the very tools they have available to them.
toby 83

What you've pointed out above OP is a genuine problem within the industry. A lot of mechanics struggle with the technology at the base level and are very quickly out of their depth when the diagnostics software doesn't return a simple component defect such as "MAP sensor Open Circuit", just for example, something that they can remove, throw away and replace.

It's not that dealerships are not training these guys, it's more that the training is not deep enough when these guys are doing their apprenticeships. I did a degree in electronic engineering and I'm lucky I did because this is the road a motor technician who wants to specialise in engine fault diagnostics should be going down. What you'll find is that any workshop, including a main dealer, is lucky if they have ONE guy who is equipped with the skill to diagnose what could be called "non-standard" engine problems, what I mean by that is that many faults are known on cars, Laguna's have coil problems, Opels have coil pack problems, Air Flow Sensor problems, etc, etc. But once your leaving familar territory and your into unknown faults or faults that need some discipline and head scratching, you will find that there is a serious shortage of skill out there...

I'm working at the moment on an internet collaboration system that lets garages post a problem and every other garage in the system can collaborate and share diagnostic experience, so over time, a whole database of real time known faults and fixes can be built up. Kind of like this forum but just for professionals...

anthony4335

The one thing I can never figure out is why these dealerships do not have any means of testing the sensors they pull out on a whimm. If it was manufactured it was tested ,so there is a way. Even if they kept a set of debug parts that would help and keep costs down. But they do not care, and that is the problem.