panicosc

Hi everyone, I own a 964 c4 1990 , with about 95 k miles , got it over a year ago.I got the car with a changed chip, the new one is a Superchips one. Since the beging the ABS alarm was SOMETIMES going on so i knew i had to repair that issue soon. The past few weeks it became permanent so decided to do some cheking.
About the same time, idle problems begun - engine dies at idle. So i connected the OBD with an interface and found some fault codes for both the ABS and the motronic.Took the car to a Bosch technician and after a week....... he decided that BOTH units DME and ABS are faulty and need repairing, he cant do these repairs so units will have to be sent abroad (im in Cyprus). I have no doubts about the ABS unit being faulty.
What i was wondering is if it is possible that the DME fault code could be a result of another reason and not the actual ecu faulty. I have read somewher that motronic fault code "41 control unit faulty "can be trigered by changing the original chip to an aftermarket one. Maybe this fault code was there since i got the car but found it only after connecting it on the diagnostic. Unfortunately i dont have a working factory chip to check this posibility or a working DME either.Just sending the DME abroad for a check its costly, let alone "repairing" for nothing. Finally, could fault 41 be trigered by any other mechanical problem? Is there a way to test and confirm this before i send it for checking/repair?
Please suggest any good repair shop for the control units preferably in EU.

Your ideas, knowledge and help is greatly needed, thanks.

dfinnegan

I had an aftermarket chip in my car when I bought it.
I had dme fault code: control unit faulty, dtc: -41-, counter: 50.
It was stated that this was likely due to the aftermarket chip not containing a proper checksum value.

I changed the chip out for a factory chip and the fault code is now gone.

dfinnegan

A search on "checksum" in the 964 forum turns up a lot of useful information.

Some interesting links:
https://rennlist.com/forums/964-1989...placement.html
https://rennlist.com/forums/964-foru...code-41-a.html
https://rennlist.com/forums/964-foru...200-473-a.html

DWS964

I had the same issue with my 90 C4 that had an unknown aftermarket chip installed. It ran fine, but had the "control unit faulty" code. I installed a Steve Weiner/GIAC chip so that I knew for sure what was in the unit, and the code disappeared.

panicosc

Many thanks for your replies and help.
Very interesting posts. Subject needs a lot of reading.
My doubt could be true. In that case the fault code 41 is only due to the aftermarket chip. This weekend I will check it with the Scantool again and compare the motronic numbers. Open the DME to see what exactly is the aftermarket chip installed and come back for some more reading...........!
So now this brings me to another question.....what are the probable reasons the engine is dying on idle if the DME is good?

klr10

Stalling during idle in my case was due to a sticking ISV. Cleaned it out with carb cleaner and all was well. The throttle closed micro switch is also a prime suspect, if it is not closing with your foot off the gas the DME doesn't know to regulate the idle speed.

Good luck!

panicosc

Scantool test.:
Motronic
Serial # 91161812401
BOSCH # 0261200450
1267356245
According to the table on the link given above, chip details correlate. Does this mean that the chip cannot be the cause? Also made the "output test" on the scantool with all 9 tests being OK.
I did open the DME and the chip is Superchips.
Tommorow will try and clean the idle valve but the fault code 41 is still an issue.
Im loosing hope........is the ecu faulty?