Custom engine harness - 5v reference issue
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Joined: Apr 2018
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Custom engine harness - 5v reference issue Hey guys! So I just finished putting a 5.3L in my 1988 Pontiac GTA. I opted to salvage a complete truck harness for my project, I was very careful I'm replacing all the pins where they came out of and it started right up! Everything seems to be working great except for 2 issues..
At the Throttle Position Sensor, I'm getting 12v at the 5v reference. It's totally messing with the signal (high idle, stuck at 20% throttle) and it's throwing codes P1635 and P1639. I already checked to make sure the wire traces back to the proper pin at the PCM. I'm wondering if it has anything to do with removing all the AC wires from the harness since they supposedly share the same 5v reference? I just don't understand how that could cause this. Anyone run into an issue like this before??
There's also a P0200 Injector Circuit code which I'm not as concerned with since it's running great with no misfires.. I'll do some more work this week to trace all the injector circuits and figure out why it's throwing that code. I just thought I'd mention it in case it could be related somehow. I confirmed getting 12v at each injector on ignition.
Thanks in advance! I'll post if I have any updates.
At the Throttle Position Sensor, I'm getting 12v at the 5v reference. It's totally messing with the signal (high idle, stuck at 20% throttle) and it's throwing codes P1635 and P1639. I already checked to make sure the wire traces back to the proper pin at the PCM. I'm wondering if it has anything to do with removing all the AC wires from the harness since they supposedly share the same 5v reference? I just don't understand how that could cause this. Anyone run into an issue like this before??
There's also a P0200 Injector Circuit code which I'm not as concerned with since it's running great with no misfires.. I'll do some more work this week to trace all the injector circuits and figure out why it's throwing that code. I just thought I'd mention it in case it could be related somehow. I confirmed getting 12v at each injector on ignition.
Thanks in advance! I'll post if I have any updates.
Thread Starter
Registered User
Joined: Apr 2018
Posts: 2
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Thanks for the response guys! I checked it out today. Before tapping into a different 5v I looked at every other pin that was supposed to be a 5v reference and I found what went wrong.. I accidentally misplaced a pin, R45 to R43.. So basically the injector #7 ground was feeding into one of the 5v references. That fixed both the codes and now it runs amazing! I was so careful to mark every pin when I was taking it apart.. didn't help that I have bad handwriting lol. Thanks again everyone.
