ECM / PROM Failure 1990-1993 Query
Thread Starter
Racer
Joined: Mar 2011
Posts: 304
Likes: 0
From: Victoria Australia
ECM / PROM Failure 1990-1993 Query
Hi Guys,
Thought I would post this for fellow C4 owners who have had issues or are having issues with electrics going strange.
Recently I got my 1990 all sorted (replacement ECM/PROM) after the car starting quitting randomly. Previously I was getting the dreaded CCM codes C41, H72 and a bunch of strange problems: defogger will only occasionally work, instant fuel use would only work so often, 1500rpm high idling or under 400rpm near stall and dash cluster going blank just to name a few.
Of course with a communication C41 link issue its hard to determine whats wrong as an OBD1 scanner cannot read anything. So for me it was a case of going back to basics with the good ol multimeter and testing and prodding.
Now, I have read many threads here and have noticed that this seems a regular problem for mid model C4s. Most have been cured with new EPROMs and/or ECMs. Seems quite rare that the CCM goes wrong and for many who garage and look after their cars, grounds and bad wiring generally are not an issue. With my issue I checked and re-checked every ground (cleaned with de-ox it) and added extra flexible plastic looming for wires that have exposed strands.
My question is, do these ECMs fail due to the location of the unit due to heat or vibration? Or is it just bad luck. Going forward, I am thinking to get my old ECM rebuilt and keep a spare EPROM.
Another question, which company that re-manufactures our ECM's are reputable?
Cheers,
Gary.
Thought I would post this for fellow C4 owners who have had issues or are having issues with electrics going strange.
Recently I got my 1990 all sorted (replacement ECM/PROM) after the car starting quitting randomly. Previously I was getting the dreaded CCM codes C41, H72 and a bunch of strange problems: defogger will only occasionally work, instant fuel use would only work so often, 1500rpm high idling or under 400rpm near stall and dash cluster going blank just to name a few.
Of course with a communication C41 link issue its hard to determine whats wrong as an OBD1 scanner cannot read anything. So for me it was a case of going back to basics with the good ol multimeter and testing and prodding.
Now, I have read many threads here and have noticed that this seems a regular problem for mid model C4s. Most have been cured with new EPROMs and/or ECMs. Seems quite rare that the CCM goes wrong and for many who garage and look after their cars, grounds and bad wiring generally are not an issue. With my issue I checked and re-checked every ground (cleaned with de-ox it) and added extra flexible plastic looming for wires that have exposed strands.
My question is, do these ECMs fail due to the location of the unit due to heat or vibration? Or is it just bad luck. Going forward, I am thinking to get my old ECM rebuilt and keep a spare EPROM.
Another question, which company that re-manufactures our ECM's are reputable?
Cheers,
Gary.
Drifting
Joined: Jun 2010
Posts: 1,853
Likes: 8
From: Westerly RI
There are several different ECM's and different locations for the years you mention. Seems to me that an ECM failure is less likely than many other electrical components.
For rebuilding:
www.autocomputersystems.com
www.autoecms.com
For rebuilding:
www.autocomputersystems.com
www.autoecms.com
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
The problem causing 90 -93 ECM's are physically identical ,have removable memcals and are located under the hood.
The later sealed case PCM's in same location don't appear to have the typical DTC 41 problems
Pre 90 ECM's not relevant as no CCM
The later sealed case PCM's in same location don't appear to have the typical DTC 41 problems
Pre 90 ECM's not relevant as no CCM
Racer
Joined: Sep 2007
Posts: 393
Likes: 0
From: Bartonville Illinois
ECM Checkout
I thought I had a bad ECM when the car was acting flacky. I opened it up and the varnish coating on the board was wrinkled from heat and cracking off.
I took it to a NAPA store and they sent it somewhere to have it checked out. The cost was around $200 total and it looks fine now and works fine.
They had me remove the e-prom module before I sent it in. It has worked fine ever since. They said you must remove the e-prom so that it doesn't get lost. or switched with another. I bought an extra e-prom and it was expensive. about $300
I took it to a NAPA store and they sent it somewhere to have it checked out. The cost was around $200 total and it looks fine now and works fine.
They had me remove the e-prom module before I sent it in. It has worked fine ever since. They said you must remove the e-prom so that it doesn't get lost. or switched with another. I bought an extra e-prom and it was expensive. about $300
