Trailer brake controller not working

Tiny
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.
Monday, July 1st, 2019 AT 9:58 AM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,512 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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Tuesday, July 2nd, 2019 AT 5:58 PM

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