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Discussion Starter · #1 ·
http://videos.streetfire.net/video/742f0a09-7f79-430d-b77c-999500eb7dfb.htm

The car seems to run fine, but I loose connections with the PCM and PT and the gauges go nuts. We have checked the entire fuse panel side of the car/wiring harnesses. Replaced the ignition switch and a few other interior checks.

We finally found if we ground the PCM to the body with alligator clips, the gauges work, but I have not tested the PT to PCM connection as my GF has the laptop today.
There is also an arc when the wire is connected.

I have some leads of it being a ground, just not sure which one or if thats even the problem.

Thanks for any input.
 

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The pcm actually has 4 grounds. They are pin #'s 16,56,57,60. They are all black w/ white stripe. They all go into splice # 106 and ground at 113. They are in the blue 80 pin connector. I cant recall where that ground is and GM SI doesnt say. I would just splice the four together and re-ground the pcm. Clear the codes if any and recheck gauge op. If they are still inop check for network communication codes IE codes that begin with U####. Let me know if that fixes the problem. It is possible that there is a bad serial data line or loose terminal but it would deffinitely set a dtc.
 

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Discussion Starter · #3 ·
Thanks man, thats the most help ive had so far. I am logging into dealerworld to see if there are any TSB's also.

I do know one thing though, its driving me crazy. :icon_eek:
 

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I checked for TSB's and saw none I also checks PI's and didnt see anything relevant. I was reading fast so it is possible I missed something. Did you have any network "U" codes?
 

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Discussion Starter · #5 ·
Connected a 4ga wire from the strut bolt to the Alternator bracket and the gauges stopped doing their crazy crap. Got 50 miles in, but now I have a new problem.. No 1st or 4th gear. Starts out in 2nd, and shifts to third fine.

Tried hooking up the PT and it wouldnt connect. So just for ****s and giggles I unplugged what I think was the data bus cable. (gray wire attached at E-brake, connector behind the carpet) And what do you know. The PT works now, and I pulled a ton of transmission codes. Like a dumbass I cleared them before writing them all down to see if it was in "limp mode" but no fix.

Before all of this:
Car was running and shifting fine and I was beginning to have the electrical gauge problems.Also, I had a small leak on the rear HG so we pulled the heads and reinstalled everything and fought this electrical issue for a couple weeks.

Its now running/driving good, idling, etc. like usual. Just no first and fourth gear.

Could this be a BCM problem? The car made 20-30 miles before the first problems started, and things seem to have gotten worse, more problems.

I have a wiring harness to try, and im still looking for bad wires and grounds, but I may look into the BCM first.
 
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