2009 GMC Sierra MAJOR Electrical Issue!

SADSIERRA1500

MEMBER
2009 GMC SIERRA
V8
2WD
AUTOMATIC
26,000 MILES

1. While idling the check engine light came on.
I have Dummy Duel Exhaust that split under the cab and then go into duels. - FIXED

2. The TPMS Sensor went out on back driver side tire. - FIXED

3. Noticed significant power surge when applying brake, turn signals or anything powered.

Now the real problem....

I was cruising down the highway with cruise on 60mph. For 25 minute drive. I came to a stop light, applie the brake, and the right turn signal, the truck then became possessed. All dash electronics lit up, blinkers, all status lights, etc. And the truck acted as though it was shutting down and starting up. Transmission was trying to stop the truck by down shifting every time the shutting down and starting up happened. I took to dealer and after a week they said they found a similiar sit. That one of the rear wiring harnesses was bad or missplaced or something. Called me after they ran 100 miles on the truck and said it was ready to go. I left the dealer went 7 miles and it happened again. Now it's back at dealer. I need some help here.

1 Reply

MERLIN2021

MECHANIC
17,250 POSTS

With 26,000 miles the dealer is the best place for it, ANY module or wiring harness should be covered under warranty. GM dealers also have the tech III scan tool MADE for GM vehicles. This will require a great troubleshooter and all his tools to track this one down, it may turn out to be a poor ground or water in a connector.