I bought my car in 2015 it is a 2010 model C220 CDI. It had travelled about 100,000 km before I bought it. A marvellous car a real pleasure to drive and that is important to me since I drive long country drives quite often. Not long after I bought it the engine light came on and would stay on for a while and then clear. I was told by the Mercedes Benz service centre that as long as it didn't stay on too long that was okay. Well it was until one day in traffic the car when into slow mode. Managed to park without an accident and called for roadside assistance. The person that attended could not fathom what was wrong and was thinking I would have two get it taken by truck back to the service centre. First I thought I would try just restarting the car and lo and behold the problem had gone. I took it to the service centre as soon as possible after that. Examining the vehicle they found at least that's what they told me that the injectors fitted were incorrect for the car, repair cost $9000. After some consideration and quite a bit of time they relented. All this time the problems were getting progressively worse but all disappeared when they replaced the injectors at their cost.

All went well fuel economy had improved and no further problems but then the engine light started to come on again. The service centre found it was the number 2 injector, so was there something wrong with their repair? The response was somewhat lacklustre and the impression I had was that no nothing more would be done. I persisted with this state of affairs properly for 12 months and then started to get some sort of fluttering noise so I took it to another specialist in continental cars. They said don't drive it home it needs a new injector and yes it was number 2. A new injector was fitted but the engine light just would not go away even though everything seemed to be in order. They tried to get a code for the injector which evidently relates to the ECU. Having had no success there they then took it back to the Mercedes Benz service centre. After a fortnight of that I retrieved the car. As a final statement they said they were waiting on a code from their major service centre.

I have taken the car now to an injector specialist. They have diagnosed the problem to be that the ECU is faulting on that particular cylinder because it hasn't been coded properly. The person I was talking to just now says for him it is incomprehensible how neither of the two service centres could not resolve the issue in a month. So advice is being looked for since this is not a problem they usually deal with. So I wondered if anyone on this forum would have some thoughts on the matter?

 

I do not know how it is possible that the ECU is faulting... do you have an aftermarket tune or something? I do not see a way the original Mercedes-Benz ECU software to be faulty. It is a software code and it is the same on every single car out of hundred thousands cars...

Generally, diesel injectors get damaged by poor-quality diesel fuel. Where are you from?

 

And $9000 Australian dollars $6700 US) to change injectors? Seriously? I can't believe it would cost that much, plus, with that low miles on the car and it being a 2015? How could the "wrong" injectors get on the car in the first place? Something isn't adding up here.

 

yes I agree subsequently the number two injector was replaced for a total cost of $1300 AUD. Which probably seems high by your terms but results from a high personal government tax which subsequently means higher wages. General Motors and Ford have withdrawn producing cars in Australia in the last few years for these reasons.

 

I live in Canberra the capital city of Australia seat of government and all that. The current mechanic is a specialist in injectors and I think he would have checked for fuel but I will doublecheck. No aftermarket tune which again since I have not owned this car for its entire life is a consideration. My own speciality is IT in the software end and what I have learnt over the years about hardware drivers leads me to believe there is something that is being missed.

 

My problem is now resolved. The engine control unit or ECM as some call it was removed from the car and sent for testing. The ECM is easy to remove but you also need the steering lock and the key assembly and that means dismantling the steering wheel and shaft plus a fair bit of the dash.

Upon testing it received a clean bill of health. That is very good in one sense since Mercedes here asks $5000 for a new one! It was returned and the car returned to the same state it was in other words still with the engine fault light and still indicating the something wrong with the number 2 injector. I thought maybe it is between the ECM and the injector but how can anything be done about it. Fortunately the auto electrician thought that also and pursued that. Checking the resistance between the injector and the ECM he found 0.3 ohms difference between number 2 and the others. As well as that the colour of one of the wires on the number two injector was yellow whereas the others were white. The wire feeding the injector at the ECM end was also white.

At sometime in the past a technician has broken the connector somehow and replaced it. It was very carefully spliced within the loom almost invisibly. Once repaired all problems have gone away!

It was quite costly for something which if known would have taken 30 minutes at Max to fix.