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93 Silverado Ecm/pcm Question

popps

By popps
in Ask A GM Technician

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popps Enthusiast

popps

Posted
Posted

Hello, I'm glad to have found this site. Hopefully you guys can help me, I have a question about my pickup and the ECM. I have checked the numbers on the ECM and the prom to verify the correct parts are installed. (Yes) The truck runs normal and idles ok with the timing wire disconnected. I did that to time it correctly, so when I stop it and plug the wire in, it runs rough and doesn't idle anymore. Is there a way to check to see if my ECM is ok, or do I have another problem I could check? It's not on the road so I couldn't drive it to the dealer for deep scanning. There are no trouble codes, so I don't know where else to look. I could possibly get a snapon scanner to check, but how much more can that do than the Actron that I already have? I am baffled with one. Any more helpful checks I could do? Certainly appreciate it.

bill190 Enthusiast

bill190

Posted
Posted

If you turn the ignition on and the check engine light comes on (then after starting it would normally go off), then this is an indication the ECM is basically working or it at least has power.

 

Other than that, there are all sorts of sensors and things connected to the ECM. I have a whole factory service manual on just this! It is called the fuel and emissions service manual and measures 3/4" thick. You get these books as well as other factory service manuals from a GM dealer (I have 4 books which came with my factory service manual set.)

 

If you want to fix these things yourself, I would suggest you get a factory service manual set for your specific year and model vehicle (from your dealer), connect everything in the vehicle as it should be connected, then in the fuel and emissions service manual, look in the table of contents for "Driveability symptoms".

 

Then turn to that page and find your symptom (such as rough idle). Then for just that symptom, there is one page of preliminary checks listed. Then on a second page is a list of additional things to check. And the entire book is filled with detailed troubleshooting and repair instructions for everything involved with the ECM.

 

Or if you want to properly adjust the timing, look in the general information area of the fuel and emissions manual. Here it lists ignition and timing. In my book, it says the timing is controlled by the ECM/PCM and regulates timing on all engines. (For my 1992, yours may be different.)

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