Trailer brake controller not working

CHRISRASKO

MEMBER
2012 GMC YUKON
6.4L
V8
4WD
AUTOMATIC
80,000 MILES

The trailer brake controller that has worked fine for the past five years. Now all of a sudden, my trailer brakes won't operate. I tested the voltage between ground and the trailer brakes at the connection plug at the rear of the truck, and even with no braking applied, there is a constant voltage that pulses between 3 and 3.5 volts. Not sure what this means, but if anyone can tell me what I should try next to diagnose this issue, it would be much appreciated. Trying to understand if there is an issue with the truck itself, or the trailer.

Thanks.

1 Reply

KEN L

MASTER CERTIFIED MECHANIC
42,840 POSTS

It looks like you have a handful of fuses and two relays that run the system, lets check those first. here are two guides and the trailer brake wiring diagrams so you can see how it works also I have included the fuse and relay locations:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

and

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

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