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Are there any clues to a bad ECM?


ken420
11-23-2005, 04:50 PM
Are there any sure signs to a bad ECM? And what portions of the old ECM should be transferred to the new one? I know the PROM is supposed to but how do I know if that is bad and causing the issue to start? Can Autozone test ECM and its respective components?

GTP Dad
11-23-2005, 06:59 PM
A bad ecm will cause drivability problems, false codes, car may not start and etc. If you think your ecm is bad then you must be having some issues with the vehicle. It is doubtful that any autoparts store can check one for you. Before spending a lot of money one you may want to find one for your model at a wrecking yard. Car-part.com can help you find one. A lot cheaper than a reman or new and if it isn't the problem you will have a spare. The only thing that will need to be transferred is the prom.

ken420
11-23-2005, 07:17 PM
Thanks for the tip GTP. Yeah I am having some issues that make no sense. Code 58 - Pass Key violation on two different keys, or it can mean a High temperature for the Transmission sensor (TTS). I can't even find that part listed in any manual. It doesn't look to be talking about my thermostat since it seems operational. And rather than start by replacing my ignition switch, or cleaning it which would still mean tearing apart my steering wheel assembly, and rather than replace sensor after sensor, I decided maybe the ECM might be faulty.
And your right if it isn't the issue I will have a spare, it just seems the easiest at this unsure crossroad I am at. I am actually hoping it is since I was having drivability issue before the 58 came. It is the latest and greatest code. My car will start and then 3 minutes or so later it dies. I felt the exhaust manifold and it does seem very warm to the touch very quickly (maybe something is backing up) but yeah I think this might be my easiest next step just to take it out of the picture.

So another question for you, would transferring the PROM transfer the problems or does it only carry the most basic info kind of like a BIOS for computers?

And have you heard of a TTS?

maxwedge
11-23-2005, 07:28 PM
Try getting to the ecm and tapping it firmly with a screwdriver handle, when running, see if the engine stumbles or stalls, common test for older GM pcms.

ken420
11-23-2005, 08:55 PM
Well no response out of the ordinary when I did this. But it is hard to tell because it starts to idle rough shortly after start so I couldn't tell if the tapping did any real effect. Something I did notice which I had forgot happened occasionally before all the more recent stalls and such. After starting the engine and tapping I saw my radio go out, and the ceiling light fluctuated. I had forgot that before my car died prompting all my repairs that the radio would go out and come back. The time would be reset as if it lost power. If it is a short how do I track it down and fix? Could it be related to the ECM? And if not could this wiring issue be causing all my problems? Maybe the shorts was causing the grounding of the transmission sensor like the 58 issue said? Any thoughts?

maxwedge
11-24-2005, 11:48 AM
Look at engine grounds especially here and /or ignition switch continuity.

GTP Dad
11-24-2005, 12:18 PM
With this new information I have to agree with maxwedge check all grounds in the car as will as the positive terminal on the battery. The ecm relies on proper voltage to work and if the voltage is bad then the computer will not work properly.

As for your other question it is plug and play. You don't need to do anything but plug in the prom and then install the computer. If you want updated engine management and etc you can purchase a new prom for the car from a dealer.

ken420
11-24-2005, 12:32 PM
Thanks for the tips guys. 'll let you know what I find. I believe I have some of the schematics in a manual and print outs from AutoZone. Do you know of any other good places for info on the web? Much appreciated.

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