Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
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I got to tell you, I'm on your side all the way, but these circuits are very complicated and not easy to diagnose unless you have a scan tool that can read data stream from the onboard computer (PCM).
Now, we could still do this even if you don't have that kind of scan tool, but you're gonna need a good voltmeter and lots and lots of patience. Are you OK with that?
Well, that's the thing; all I've got on the way of "written instructions" are the diagnostic procedures GM technicians use and that would require you to have the same tools and equipment as they do. What I was hoping to do was to "translate" the process based on bits of information you could get using just a multimeter as we went along.
In any case, I would not recommend replacing any parts without first diagnosing the issue - being that this vehicle has the Police options, guessing can get very expensive in a hurry.