Mercedes C220 CDI 2012 (C204) EIS/Key Issues

[Thamid12345]

Hi All,
Hope you are well and are keeping safe.

I have an issue I'd like your advice on, on my Mercedes C220 CDI 2012 Coupe (C204).

Since quarantine, I have been doing very little long distance mileage and my DPF got completely full with Soot and went into Limp mode where it lost most of its acceleration. My local garage advised me that the best thing to do would be to remap the ECU with DPF delete and would also remap the car to give some performance/fuel economy gains.

Another issue that I have (maybe 10% of the time) is that the key, when inserted into the module, causes the 'Key Not Recognised' issue to appear on the car, however it always starts, and since it happened so rarely I had not been so active to get it sorted. I also have some very minor instances where the car will not unlock/lock, although this is quickly resolved by pressing it a few times. This made me think that this was an issue with the key itself.

It just so happened that as the car was being remapped and the key was put into the ignition, it was on this off chance that the key was not recognised and the map did not work at all and thus the car would not start. After some fiddling about restoring the old map, the car started, but would not start the next day. It was subsequently fixed, with the diagnosis being some sort of wiring or module issue. I am due to give the car into the garage in the next week or so to get this fully checked, but I would love to get your opinions on what you think the issue is.

Do you think it just may be an issue with the key? (At the moment, I don't have a replacement to check this with), an issue with the EIS module, or something completely else?

The tuner is very reputable in my area and so I do not think the map itself is the issue but would love to hear your thoughts.

Thanks so much in advance.

 

[markjay]

...My local garage advised me that the best thing to do would be to remap the ECU with DPF delete...

Welcome to the forum.

No, it's absolutely not the best thing to do, it is illegal, it's an MOT failure, and it's polluting. The best thing to do is remove the PDF and clean it, or failing that replace it with new.

But yes, it is a common thing to do... your call.

 

[markjay]

....Do you think it just may be an issue with the key? (At the moment, I don't have a replacement to check this with), an issue with the EIS module, or something completely else?...

Unfortunately it's nigh-on impossible to diagnose an intermittent ignition issue that leaves no fault codes. The garage could have the car for a week and not be able to replicate the fault. And similarly you can't really eliminate the key as the cause without testing with a spare key.

That said, EIS failure is common. Sadly replacing the EIS is expensive (£400+), and cutting a spare key is expensive as well (£200+).

I would start with having a spare key programmed (I wouldn't be happy driving a car that has no spare key anyway).

On another note, the key is made of two completely separate parts.

For starting the car, there's a passive transponder (tiny chip that does not require battery power). For locking the car and for rolling up/down the windows, there's a radio transmitter and infrared led, both of which use the battery.

So having problems with the locking/unlocking bit of the fob does not necessarily indicate a problem with the passive transponder. The car should start OK even with the batteries removed from the fob, for example.

 

[Thamid12345]

Unfortunately it's nigh-on impossible to diagnose an intermittent ignition issue that leaves no fault codes. The garage could have the car for a week and not be able to replicate the fault. And similarly you can't really eliminate the key as the cause without testing with a spare key.

That said, EIS failure is common. Sadly replacing the EIS is expensive (£400+), and cutting a spare key is expensive as well (£200+).

I would start with having a spare key programmed (I wouldn't be happy driving a car that has no spare key anyway).

On another note, the key is made of two completely separate parts.

For starting the car, there's a passive transponder (tiny chip that does not require battery power). For locking the car and for rolling up/down the windows, there's a radio transmitter and infrared led, both of which use the battery.

So having problems with the locking/unlocking bit of the fob does not necessarily indicate a problem with the passive transponder. The car should start OK even with the batteries removed from the fob, for example.

Hi,

Thanks alot for your prompt and detailed response.
Really appreciate your advice.
I'll arrange to get a spare key made definitely. It was on my to-do list, and certainly fast tracked with this issue.

On the point you made regarding the passive transponder, in all instances the car would always start (whether it read as key not recognised or not) it was only once the car was remapped that it would not start. To clarify, the car would technically start but almost immediately die out, and then upon starting it again would chug but not start. If I left it for 20 minutes and came back those 2 steps would happen again.

Since the car would always start (with the exception of the day after the remap) after reading on the issues people have had with EIS (where the car does not start at all), I thought maybe this would not be an EIS fault, but rather the issue was that:

1. The key itself has some faults and needs to be repaired.
2. the remap was loaded whilst the key was in the car and 'not recognized'

Thanks again for your thoughts and looking forward to your further insights.

 

[markjay]

Hi,

Thanks alot for your prompt and detailed response.
Really appreciate your advice.
I'll arrange to get a spare key made definitely. It was on my to-do list, and certainly fast tracked with this issue.

On the point you made regarding the passive transponder, in all instances the car would always start (whether it read as key not recognised or not) it was only once the car was remapped that it would not start. To clarify, the car would technically start but almost immediately die out, and then upon starting it again would chug but not start. If I left it for 20 minutes and came back those 2 steps would happen again.

Since the car would always start (with the exception of the day after the remap) after reading on the issues people have had with EIS (where the car does not start at all), I thought maybe this would not be an EIS fault, but rather the issue was that:

1. The key itself has some faults and needs to be repaired.
2. the remap was loaded whilst the key was in the car and 'not recognized'

Thanks again for your thoughts and looking forward to your further insights.

From the symptoms you describe, it does not sound like it's the EIS or the key....

If it happened after the remap, then the remapper would be your first port of call - they can temporarily restore the original map and see if this resolved the issue.

And of course it could be just a coincidence that some other unrelated part just happened to fail while the car was being remapped.

 

[Thamid12345]

From the symptoms you describe, it does not sound like it's the EIS or the key....

If it happened after the remap, then the remapper would be your first port of call - they can temporarily restore the original map and see if this resolved the issue.

And of course it could be just a coincidence that some other unrelated part just happened to fail while the car was being remapped.

Thanks Mark,

You're absolutely right, as I mentioned once the original map was put back on, the issue was resolved.
I'm going to get a replacement key in any case and get the EIS checked to make sure its not faulty either. Hopefully that will stop the 'Key not recognised' to stop popping up again.