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Amedee
Amedee, GMC Technician
Category: GM
Satisfied Customers: 26414
Experience:  ASE certified tech with advanced level specialist. Wisconsin certified emissions state inspector
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my trailer connector..points for me to check the wiring

Customer Question

The contact for the back up lights in my trailer connector is not showing 12 volts when in reverse. I checked the fuse for the trailer back up lights and it is good and shows 12 volts when the truck is in reverse. Besides the connector at the very bak of the truck where else are there any points for me to check the wiring. I know it's the light green wire in the harness.

Sierra 2500HD 4X4
Duramax diesel
Submitted: 6 years ago.
Category: GM
Expert:  Amedee replied 6 years ago.
Hello!

Did you still need help?

Would you like a wiring diagram for your trailer lights?
Expert:  Amedee replied 6 years ago.
There are two fuses to check. The B/U LP 20 amp fuse and the TRL B/U 10 amp fuse. Be sure to check to see if these fuses are not only good, but be sure that they have power to them with the vehicle in reverse. You should be able to do this just with the key on and shifter in reverse.

Here is a wiring diagram.


graphic
Customer: replied 6 years ago.
I checked both fuses and they are good and energized when the truck is in reverse. There is an interface to the trailer connector in the back of the truck between the trailer connector and the wiring harness. The light green is dead there too. Is there another connector between that point and the fuse panel under the hood? Was the back up alarm a standard feature on this truck? If so is there a place where the wire would commonly have been cut to disable the backup alarm?

Besides the wiring diagram is there a cable routing diagram which would show where in the chassis these cables are run and where any interface connectors might be?


Thanks.

Scott
Expert:  Amedee replied 6 years ago.
Scott,

Are you saying there there is power on both of these fuses but just no power to the trailer connector on the light green wire?
Expert:  Amedee replied 6 years ago.
Here is a wiring diagram from that fuse to your trailer connector. There are a few points or brakes/splices that you can test or check for power at to determine which ones do or do not have power. This will help you located your open or break in the wire.

graphic
Expert:  Amedee replied 6 years ago.
Here is a better picture.

graphic
Amedee and 2 other GM Specialists are ready to help you
Customer: replied 6 years ago.
That's correct, there is power at both fuses (on both sides of the fuse) when the truck is in reverse. I'm guessing it has to be at C3 because it's dead at C428 If C3 is good there has to be a break in the wire somewhere.

Thanks for your help, the wiring diagrams helped out.

Expert:  Amedee replied 6 years ago.
YUP!

You got it!

THanks for the accept!

Let me know what you find!
Customer: replied 6 years ago.
I spent about two hours trouble shooting and tracing the problem. The problem was in the trailer connector in the back of the truck. It is a two piece connector and when it was assembled the center pin was bent over out of position. I straightened the pin and reassembled the connector. That solved the problem.
Expert:  Amedee replied 6 years ago.
Hello!

EXCELLENT!

Glad to hear it is fixed!

Feels good huh?

Have a great day!