I have a 1994 E320 non-ASR California car. 222k miles. The engine wiring harness was replaced with factory Mercedes harness by me over 7 years ago. 2 months back I replaced the ETA which was dead for almost a year. The car was driveable before but with no throttle assist when turning on the AC it was a safety/stalling hazzard. So with summer coming I replaced it with a used unit and all was good. Then about a week ago the car went into limp home mode. It starts and idles fine but will not rev past 1500 rpm. I checked codes (Arthur Dalton code reader) and got the following:

Pin 3: 17
Pin 8: 42,45
Pin 14: Cannot read codes, led is dim with no button push

This all pointed to the CC/ISC module N4/3 since I could not pull any codes from it. So I located another module, 124-545-55-32 and it is showing the same issue. I am assuming something along the path has a high resistance short to ground producing the dim led on pin 14 but I am not sure where to go next. I am thinking I can start disconnecting other inputs into N4/3 and see if I can get the dim led to go away. But I am not sure where some of the connectors are. Such as X81/4. It is listed in the W124 Electrical Troubleshooting Manual on StarTek but no location is given for it.

http://www.startekinfo.com/StarTek/outside/12264/Program/ETM/wire_plug.pdf

I will also be checking the OVP and diagnostic modules. Especially getting the info on which version the OVP is as I know these cause many strange issues.

So I am hoping someone might have an idea to help reduce my search. I have been Googling for hours with lots of information but nothing in my specific problem area.

Thanks,
David