I replaced both of the cam magnets and the did the pigtail update. Tried cleaning the wiring harness to the ECM several times, no luck keep getting the cel back. Does anyone have the procedure for replacing the wiring harness or a video on doing it? Ive tried YouTube and not finding anything on this specific engine? Thank you guys

 

Welcome! How do the cam position sensor connectors look? And the O2 sensor connectors?

 

Both of the cam magnets were drenched with oil.I replaced them & installed pigtail update (The oil made it all the way to the ecm though)Trying to find a step by step or video on replacing the harness? Thanks

 

Yes, understood that you changed the magnets and installed pigtails. What about the cam position sensor connectors and the O2 sensor connectors? Have you inspected these connectors for oil?

 

Thanks chassis. I see what you're saying. On mine I'm getting Trace amount of oil and that rear ECM connector and I've cleaned it with CRC electrical cleaner about 8 different times and the CEL will sometimes stay out or a month and then come back on I will check that connector and there will be a trace amount of oil again on the pins. These are some of the codes that come back every time. Would you think it would still be worth checking the connectors at the cam position sensor and O2 sensors?thanks guys

 

Sorry to see the continued oil on pins. The permanent corrective action appears to be replacing all of the parts: cam position sensors, cam magnets, wire harness and ECU. And O2 sensors if they have been contaminated.

There seems to be some lack of consensus on the root cause of this situation. The notion of biodegradable wiring insulation has been proposed as the cause.

@BlownV8 @arsupisemnet What do you make of this situation? Biodegradable insulation, or oil wicking through the harness? Neither? Both?

 

hi chassis. I took a look at my cam position sensor connectors and O2 sensor connectors and the cam position connectors had a lot of oil in them. None in the O2 sensors connectors and this time dry in the ECU connector. Do you think it would be worth trying a clean (crc electrical cleaner) on the cam position sensor connectors?Thank You

 

It is my understanding that wire loom of biodegradable materials, or less than ideal automotive under hood materials ended before 2000. This should not be an issue.

 

Spraying the connectors with CRC contact cleaner is a minimum first step. Next is replacing the failed parts, which are the cam position sensors and cam magnets.

Because oil has reached the ECU, it can be safely assumed that the harness wiring is contaminated. The next step is likely to replace the harness, unfortunately. It seems to me a high probability that oil would continue to migrate into the ECU, even if the leaks were stopped and all connectors were cleaned. There is still oil in the harness and it will go wherever it wants to go.

The final step, if harness replacement doesn't succeed, is to replace the ECU. A dealer or indy would be needed to code the new ECU to your VIN.

 

If you have not done so already, I recommend that you consider disassembling the connectors that plug into the ECU. Here’s a thread with information: https://mbworld.org/forums/c-class-w...obd-codes.html

 

Thanks Chassis. With all my research on this I thought that the main source of the oil in the harness was from me cam magnets. Are you saying that the cam sensors are a source of the oil getting into the harness also?
Picture of my new cam magnets with the pigtail update.

 

What is the pigtail update? I also replaced my cam magnets because they were leaking oil along with my vacuum pump... It is very likely I too have oil in the harness. I well check tomorrow..

 

@Ptully Yes, some posters on this site have observed oil in the cam position sensor connector.

 

FWIW, Chassis is correct. The cam position sensors were the issue with the oil leaking on the W203. This is exactly what happened to my W203. I had the CPS changed under TSB when the car was still in warranty back in the late 2000s. Everything seemed to be okay - but I would get an occasional rough cold start and idle that would go away within the minute. In 2017 I ended up taking my car in for an oil change at the dealer because I had a discounted oil change - car had always had random CEL pop and then go off (I can't remember the codes but I believe they were misfires). The dealer basically told me what I already knew about the CEL. Said that these vehicles had issues with the CPS leaking oil into the main harness and then traveling to the ECU. I informed them that I knew about it and there really isn't anything I wanted to do because the cost wasn't really worth it on a 13 year old car. They ended up calling MBUSA to see what they could do to possibly get this done for free. They couldn't get it done for free but they were able to get a significant discount for the job. Price I paid to get a completely new main wiring harness, ME, MAF, and labor was $800 at the dealer.

I ended up doing it just because this was my daily driver and I was somewhat sick of the issues since the late 2000s. The original quote was around 4000. I still have the car and it runs great mechanically. Some suspension components need to be changed but thats due to Michigan roads and some negligence on my part of not replacing parts sooner.

I could have tried to do some more investigatory cleaning of the ECU/ME and the wireharness, but I figured even if I cleaned off the ME, any oil left in the harness would travel back to the ME and we would be back to square 1.

 

part number 27115 0025605 for the pigtails as in my picture they plug into the cam magnets .If the new cam magnets go bad (start leaking)they will stop the oil from wicking through your wiring harness

 

Gotcha I replaced the cam magnets because they where leaking... I however did not replace the pigtails... Should this have been done? I did clean them with electrical cleaner when I replaced the cam magnets..

 

yes I would replace the pigtails , they are pretty cheap insurance. Also a great idea is to check and clean the cam position connectors and O2 sensor connectors as advised by (Chassis) . My CEL has been out for a month now since I cleaned my cam position sensor connectors

 

I have the majority of connectors disconnected because I had to remove the supercharge all of them well be cleaned prior to reconnecting...

i'll buy the pigtail looks like pelicanparts has them for $26 I might do them when I replace the drive belt pulley which should be in the next week or 2

Thank you

 

It's from Oil wicking down the wiring loom from the previously leaking Cam Sensors to the ECU. A common problem with Mercedes and fundamentally a bad design fault. If one doesn't replace the entire wiring harness (expensive) which is already contaminated with oil then the same problem will reoccur ultimately damaging the work and parts you have already fitted.

 

It's from Oil wicking down the wiring loom from the previously leaking Cam Sensors to the ECU. A common problem with Mercedes and fundamentally a bad design fault. If one doesn't replace the entire wiring harness (expensive) which is already contaminated with oil then the same problem will reoccur ultimately damaging the work and parts you have already fitted.