2000 gmc sierra 2500 7 pin trailer stop lamps will not work

jburk410 · August 22, 2014

2000 gmc sierra 2500 7 pin trailer stop lamps will not work. so i hooked up a new 7 pin trailer socket and everything works fine except the actual stop lamps. i have running lights and blinkers. it was my understanding that the blinkers run the stop lamps but maybe i'm wrong. I've checked all the fuses and they are fine. the ground is good, there are no wires chaffed and i get a stop lamp signal for the third brake light. I've tried multiple trailers and even a test light, I'm starting to go crazy. Does anyone have any suggestions?

gmtech4 · August 22, 2014

get a schematic and start from the beginning ,follow the circuit ,if it makes no sense to you ,,,,hit up a shop

Doug_Scott · August 22, 2014

You may already know this, but since you did not actually say it, I will, just to be sure you know this. The issue is not in the trailer, it is in the truck, and as suggested above, you need to locate the wiring diagram, and start checking for power in the brake light circuit. Start at the rear of the truck, and follow the harness to the front of the truck, checking for power at each connector that the wire passes through. I suggest starting from the rear simply due to the wiring being exposed to the environment for more than half its length. If you are a follower of Murphy's Law, start at the end you would not normally start from.

I have used this site a few times for reference. http://www.etrailer.com/faq-wiring.aspx. You can use it to determine which wire in the 7 pin connector does what.

bossier62guy · August 22, 2014

2000 gmc sierra 2500 7 pin trailer stop lamps will not work. so i hooked up a new 7 pin trailer socket and everything works fine except the actual stop lamps. i have running lights and blinkers. it was my understanding that the blinkers run the stop lamps but maybe i'm wrong. I've checked all the fuses and they are fine. the ground is good, there are no wires chaffed and i get a stop lamp signal for the third brake light. I've tried multiple trailers and even a test light, I'm starting to go crazy. Does anyone have any suggestions?

You are correct that the turn signals and brake signals use the same wires (yellow & dark green). Since the turn signals work properly that pretty much rules out a wire or ground being the issue. If the truck brake lights are working you probably have an issue w/ the turn signal/hazard switch or possibly the wiring going to it. schematics.pdf

trailer.pdf

schematics.pdf

trailer.pdf