Yes I have ran into quite a few times where as it came down to a faulty PCM or wiring issue or alternator. no particular failure seems common. You need to run some testing on the wires using the below test, starting with section B.
Also if needed here is the wire diagram.
If you get held up on any of the tests, just let me know and I will help you through it. I feel your going to find this to be the PCM since it has been checked out already and they seem to be avoiding mentioning the computer controlled charging system.
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