Replacement 7-Way and 4-Way for 2003 GMC Sierra With Factory Tow Package

Updated 10/02/2020 | Published 09/30/2020

Question:

Hey my name is Larry, I am having lighting issues. I have been having problems ever since I spilced into my factory trailer lights hookup at the time I didnt know it was equipped with factory trailer lights. The hookup is a 4 prong flat for boat trailer... which is right for what i need. But I believe it is causing problems with my vehicle.. whenever I apply my brake on the vehicle my turn signals on both sides flash back in forth the lic. Plate light also flashes. The only brake light I have is on the cab. I have tail, and correct turn signals until I apply the brake, then it all goes to hell. I am going to try and send a pic or two. Any suggestions

asked by: LARRY G

Expert Reply:

So it sounds like you spliced into the factory trailer wiring harness of your 2003 GMC Sierra's factory 7-way, or factory tow package harness. Doing that would cause the issues you are having so what you need to do is replace the harness with the Replacement Custom Multi-Tow 7-Way and 4-Way Trailer Connectors # 30955.

This will work without anything else so long as you didn't try and splice into the wiring AFTER the truck's factory plug. If you spliced the wires after the plug you will need to have it repaired at your local dealer to be able to use and plug in the replacement connector.

expert reply by: Kyle S