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04 GTO P59 PCM, harness, and 76mm turbo 370 LQ4 in a Nissan 240sx....i can provide more if needed.
I've been driving it off and on for the last few years and it's been fine, other than troubleshooting cooling issues with my setup. This past Friday i drove it around for a bit and parked it in my garage, came back an hour later to move it and while cranking i noticed smoke from under the dash.... PCM is currently on the passenger floor.
I immediately hopped out and disconnected the battery and started to inspect. Turns out, the Green connector Pin 61 - Purple wire (bank 2 coil - low reference) was melted.
I'm in the process of pulling the harness out to inspect further. Here are pics of the PCM connector as well as the 7 pin coil plug that show damage. I'm pulling the coil sub harness to see how the individual coils look.
Has anyone seen anything like this and what a possible cause might be? I haven't seen anything related in a search, but it seams weird a for a low reference wire.
You would think a fuse should have protected the wire from that much current.
Rick
Thanks, but it's a low reference wire and is not hot. the circuit is straight from the PCM to the coils, nothing else. attached diagram from the service manual
Do you think it's possible that the low reference wire shorted on a hot wire somewhere? If not that, then I would suspect that maybe one of the coils has shorted out somehow allowing current to hit that wire.. One of those two, or the PCM is bad internally. Since the wire melted all the way back to the PCM, I'd suspect internal damage to the PCM, but the problem *might* have started elsewhere. Please post back and let us know what you find the problem is/was..
So I’ve torn the harness apart from the com all the way to the passenger coil harness connector and I haven’t found any other wires that have broken through. The sub harness connector to the individual coils are fine. However I did fine something that was more disturbing and glad the damage wasn’t any worse than this. Not sure if this caused the melted low ref wire or not.
main 0 gauge battery cable to started melted through. It was not touching anything so it looks like it was heat from the #8 cylinder. I’ve made a new cable and have some DeI fire sleeve on the way before I rewire the the harness.
The rest of the car car is apart for a new radiator and fans and possibly an a2w intercooler/water box setup, so it’ll be a while before I can report back on the status
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melted coil low reference wire 
