Just got back from what seems like a wasted 3 hours at the local Isuzu dealership. I've been having problems with high (and irratic) idle and the check engine light staying on. I've done darn near everything there is to do to correct the problem and now the Isuzu tech tells me my PCM (Powertrain Control Module) is overheating and needs to be replaced. I've never heard of the PCM, is this the same as the ECM? Would it effect idle if overheating? He quoted me a price of $183.00 for the part.

All help is greatly appreciated.

First off, it would help everyone on the forum if we knew what kind of truck we were talking about here. But yes, pcm and ecm are one in the same....(if history serves me right).

ECM (Electronic Control Module)is what the main computer was called before 1996 (I believe).

PCM (Power-train Control Module)is what those same computers are called now after government regulated a whole bunch of terminology with regards to computers and OBD ll codes (trouble codes)mostly from 1996 and later.

But here's the thing about your situation. You say the Isuzu tech said that your PCM is overheating? I would want to know why it's overheating before I went out and replaced it. I have an '89 with the original ECM and (knock on wood) even after all these years, it still works fine. These computers are not usually delicate or prone to overheating. I mean, who's to say if you replace it that the new one wouldn't just overheat as well. Without knowing the source of the problem, it could happen. I would definitely get a second opinion.

Personally, if you have a college near-by with an Automotive curriculum, I would go and ask one of the instructors for advice on this. Most instructors are there because they have years (20 to 30 in most cases) of experience and a good deal either own or have owned a service garage. Automotive curriculums usually have an "Automotive Electronics Instructor" who would probably be the best for the advice you are seeking. Once again, that is my personal opinion but it has worked for me in the past....many times.

Hope this helps...good luck...

dawn...

Thanks for the info. My truck is a '90 Trooper with the 2.8 and manual tranny. New development last night, one of the fuel injector probes caught on fire last night and melted and belched a lot of smoke out. I have never had any sort of problem with the fuel injectors until this dealership laid hands on my Trooper to "diagnose" a high idle. I'm really upset.

Additional info, the tech said I needed a new Throttle Body, cost $1,416.60, a new EGR Valve (has one that is less than 6 months old and is working fine) cost $53.00, a new Distributor (says it has excessive play in it) cost ???, says he can't even order one. And of course the new PCM.

After asking him if he guaranteed that this would fix my problem (although I wasn't really considering the work since my Trooper cost me $1,300 total), he said "it should", but he couldn't guarantee it.

Getting a distributor should be no problem. You should be able to pull one from any chevy blazer or s-10 with the 2.8. $1400 for a new throttle body is quite excessive considering you can get one from a junkyard for about $40, or a new Holley unit for less than $400. I would try another dealer or private mechanic.

Dan

1. Run away from the person who is giving you this advice and quotes.
2. Buy a Haynes and Chiltons Manual and study it
3. Get the codes your truck is making by directions in Haynes Manual
4. Concentrate at the codes versus than just throwing fixes at it.

Just to clear things up, here is a post about these problems from a few months ago 2.8 Problems.

The only code that the ECM has ever thrown is 44 or "lean condition". I have had the trooper at 3 independent garages, all of which "specialize" in foreign cars and are ASE certified. None of them have been able to fix the problem. I can't imagine that this could be anything very complex to fix, but no one has been able (or willing) to diagnose the problem.

I have a Haynes manual and it has been gone through throughly, cover to cover. I have done everything the manual has suggested to do and much more with no fix found yet.

Im still leaning towards a manifold gasket leak. Im guessing at the base of the throttle body. After having done all this work, have you reset the computer? If its throwing a lean code, your getting a lot of air from somewhere. Can you hear what sounds like air rushing anywhere from the motor? Or maybe even a whistle?

Dan

Check for that manifold leak (or any other air leaking in AFTER your mass airflow sensor) by spraying some starter fluid at various spots around the intake manifold/other air tubing.. If the engine races while spraying, you are getting extraflow after the MAF sensor and this could account for your lean condition.
Side note... I have had similar experiences and if I could manage to never take a vehicle to a mechanic again, I would be a happy man.. It's not their vehicle and the vast, vast majority will not put the necessary time/diagnostics into the job and will just throw fixes at it until you go away (probably because you are now broke).

Good luck!!

JD

He's got a TBI 2.8 so no MAF. The carb cleaner trick will still work though.

The intake manifold gasket was replaced a few months ago when the coolant began finding its way into the engine oil. So we have eliminated that as the culprit. I'm running out of thinks to try. I have yet to find a competent, conscientious mechanic who will spend the time and effort to correctly diagnose and correct the problem my Trooper is suffering from.