PCM Batt orange wire at 3.2V
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Joined: Nov 2025
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PCM Batt orange wire at 3.2V New here, but I'm struggling to troubleshoot my wire harness.
This is an off-road buggy, running a LQ9 mated to 4L60e, I have over 460 hours of run time with this setup. I've done 3 different LS swaps.
On the last trip out I dropped off a ledge and landed pretty hard. Engine died. Tried to re-start and fuel pump wasn't turning on. Ended up hard wiring in the fuel pump to get off the trail. On the way back to camp someone in front of me was overheating and I shut my rig down while waiting - and then it never started back up (even with hard wired fuel).
I've narrowed the problem down to the "PCM BATT" fuse which is the 12V supply to the computer. When that fuse is in, the six fuses in that bank of the fuse block all drop to ~3.2 volts. I just tried a different PCM (my last resort) and it does the same thing with that computer. It's the bottom right fuse in attachment. Any ideas what could be causing the voltage to drop when i plug that in?
This is an off-road buggy, running a LQ9 mated to 4L60e, I have over 460 hours of run time with this setup. I've done 3 different LS swaps.
On the last trip out I dropped off a ledge and landed pretty hard. Engine died. Tried to re-start and fuel pump wasn't turning on. Ended up hard wiring in the fuel pump to get off the trail. On the way back to camp someone in front of me was overheating and I shut my rig down while waiting - and then it never started back up (even with hard wired fuel).
I've narrowed the problem down to the "PCM BATT" fuse which is the 12V supply to the computer. When that fuse is in, the six fuses in that bank of the fuse block all drop to ~3.2 volts. I just tried a different PCM (my last resort) and it does the same thing with that computer. It's the bottom right fuse in attachment. Any ideas what could be causing the voltage to drop when i plug that in?
Teching In
Joined: Jan 2025
Posts: 22
Likes: 3
From: USA
That sounds like a dead short to ground on that PCM BATT wire. The hard landing probably pinched a wire or crushed a connector. Don't keep plugging in PCMs, you could fry them.
You need to unplug the main engine harness from the PCM and see if the voltage comes back to 12V at the fuse. If it does, the short is in the engine harness. You'll have to visually trace that orange wire, especially where it runs near the frame or firewall, looking for damaged insulation.
You need to unplug the main engine harness from the PCM and see if the voltage comes back to 12V at the fuse. If it does, the short is in the engine harness. You'll have to visually trace that orange wire, especially where it runs near the frame or firewall, looking for damaged insulation.
