GMC Troubleshooting Questions? Ask a Mechanic for Answers
My name is ***** ***** I am a professional here at Just Answer. I noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.
My info is limited on your model here but I see no one else has responded and thought I would see if I can help here.
If this model has any trailer wiring on it check the trailer wiring for any electrical damage at all.I have seen in several cases before where shorted or damaged trailer wiring will cause this type of fault here needing repaired to correct this issue.If this has no trailer wiring or this was already checked and found to be o.k. let me know.
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O.k.,thats where I would start as this is usually most common.Check for any corrosion at or near the trailer plug and any inline connection harnesses as well.Make sure any ground to frame wires or body grounds are secure as well at the rear trailer wiring area.
If you turn the turn signal on and off while pressing on the brake pedal do the brake lights then work or try and work at all then?