Is there a Standard Wire Color and Function Code for a 7-Way Trailer Connector on a 2005 GMC Sierra

Question:

Im using your wiring diagram shown on your website but my truck does not have a white wire i can use as a ground. Did they possibly use other color wires on the 05 gmc?

asked by: Bill S

Expert Reply:

Yes, there is no standard wiring color code so the wire functions could be anything. The only way to know for sure is to test the wires using a circuit tester such as # PTW2991. The ground will not have any voltage on it, or at least it should not unless there is a short to ground.

The other wires will show power when the function associated with each one is activated (running lights, left/right turn and brake lights, reverse lights, 12 volt power which could be on all the time, and output from a brake controller). The one that does not have any functions would then be the ground by process of elimination.

The color wires shown in the diagrams in the linked help article are the common colors used for functions but are not standards. Testing is important to make sure you get the correct wires in the right spots on the back of the connector.

expert reply by: Michael H