P.L. Error Code and Cargo Lamp Lights Up Using Primus Brake Controller on 2002 GMC Sierra

Question:

P.L. displays and cargo lamp lit on back of cab on a 2002 GMC Sierra truck. New 7-pin socket was purchased and wired and checked with a meter to be wired correctly. The Primus IQ was purchased with a 2002 GMC Sierra harness for the brake controller. New installation of black and white wires for trailer power supply and white wire ground. Any suggestions?

asked by: Steve F

Expert Reply:

The PL indicates that there is a power interruption when the brake controller is supposed to be activating the trailer brakes. The fact that the cargo lamp comes on indicates to me that the red wire on the brake controller is connected to the wrong circuit.

The harness you should be using is # 3025-P. Note the location of the red wire and compare it to your harness and red wire. If the red wire on your harness is in a different spot you will need to move it to the location shown in the picture.

I have included a link to our FAQ article on troubleshooting brake controllers that might also help.

expert reply by: Michael H