Troubleshooting Brake Controller Stoplight Circuit Not Having Voltage on 2002 GMC 2500HD

Question:

It appears that I am not getting any voltage to my brake controller red wire when vehicle brake pedal is pushed. I have checked all related fuses that I can find. Vehicle brake lights work. 2002 GMC 2500HD with a new P3 brake controller. The controller powers up and senses the trailer is connected. Troubleshooting screen on P3 shows no input voltage from truck, verified with volt meter.

asked by: Terry T

Expert Reply:

Check the third brake light fuse under the hood of your truck labeled CHMSL. On your generation of GM truck anytime the problem you described comes up the issue is the fuse being blown.

You can easily check to see if this the problem by checking to see if the third brake light at the back of the cab of your truck lights up when you step on the brakes. If it doesn't light up the problem is the fuse. This circuit is notorious for being easy to blow on your truck.

expert reply by: Jameson C