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Given that you've already listed most of the items I'd default to checking, I have two considerations: intermittent harness problem (probably power or ground) to the PCM, or a module such as the cluster internally faulted and sending garbage data to the PCM it doesn't know what to do with/interfering with the PCM's power somehow. If the PCM does control the alternator voltage, and the voltage regulator circuit loses power, I'm guessing it would just cease regulating and your voltage would skyrocket. You say the PCM tests good, have you actually tried a new PCM to see if the problem persists? If the voltage regulator has an intermittent failure allowing the voltage to go that high it could very well cause all sorts of persistent and infuriatingly nonsensical problems all over the vehicle.
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Mar 11, 2020 03:46
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| # ¿ May 22, 2024 13:41 |
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The nature of all of the faults scream power, ground, or control issue to me. I'm leaning on the PCM or PCM harness being at fault. Does the PCM have to be programmed or is it a straight drop-in?
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Mar 11, 2020 11:38
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Krakkles posted:Annnnnd, nope. Oh, what a disappointment. I thought being at least partially confident was ok. Well, for a full harness check, I'd start at one place - probably the PCM - and just check along the whole harness with my eyes and hands. If there's no easily detectable trouble spots (chafe points, suspiciously flexible or stiff sections) I'd probably start trying to unwrap the harness. That is the lovely time consuming part and might again not turn up anything actionable. Wiring problems, especially intermittent, usually won't be uncovered by continuity checks. If there's an intermittent short between a power and signal wire, continuity checks to ground from the PCM end of the harness will be good and won't turn up anything suspicious. There is the potential of something else on the PCM's 12v input line loving up and causing a voltage drop that is enough to trip the PCM to shut off momentarily. Are you able to post the PCM wiring harness diagram, with its power inputs and grounds?
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Mar 19, 2020 12:58
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What a hell of a find, I've located a few similar looking culprits and the immediate gratification and confidence that moment inspires is indescribable. Glad you found it. As for credit, anyone could suggest a harness problem - it's kind of catch-all and that was pretty much my only contribution because i got here first  if votes matter then charitable donation, absolutely - I tend to lean towards "your local dog rescue/no-kill shelter" as my suggested recipient.I'd also second Ferremit's suggestion of just lopping off that leg of harness and splicing the whole thing in, which will make for one splice per wire instead of two after having spliced in a mismatched wire. I understand your preference to maintain social distance though and applaud your willingness to dive in and tackle it. It may seem slightly daunting, but I'm glad you said you're basically comfortable with it - think of it as just a wire splice, which you've done a million more times - but a bunch of em. Piece of cake. Continuity check as you go if you get antsy about anything.
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Apr 2, 2020 04:16
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Krakkles posted:In a moment of genius, I donated to my local shelter without checking that they were actually no-kill, because I thought they were. Turns out they're not. I'm searching to find an actual no-kill and will match the donation there, and hopefully this lets this one keep some alive a little longer also. Hopi likes your suggestion: Thank you for this. I like Hopi. 
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Apr 2, 2020 14:15
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