Troubleshooting N.C. Error Code on a 2004 GMC Sierra 2500 with Trailer Connected  

Question:

Expert Reply:

The n.c. means that your brake output circuit is not complete. This is normal to see for a few seconds of turning your vehicle on without a trailer connected. If your trailer is connected there is an error on the brake output circuit. The first place I would look is in your trailer connectors. Most likely there's corrosion there and cleaning it will fix the problem.

Other possible issues could be that the brake output circuit on your trailer is shorting out somewhere. Basically the problem lies somewhere between the back of your brake controller on the blue wire following that circuit all the way to the brake assemblies. What you could do to narrow down the problem is test the brake output circuit on the trailer connector (5:00 pin) of your 2004 GMC Sierra. Use a circuit tester like our part # 3808 while a buddy applies the manual override of your brake controller.

If there is voltage there then you know the problem is in the trailer wiring and would need to be inspected. Make sure the assemblies are grounded to a clean metal surface as well.

If there isn't voltage there then you know the problem is on your truck. The next step would be to sever the blue wire of the brake controller about 6 inches from the brake controller, leaving enough wire to reconnect if needed. If the controller now has output on the controller side of the wiring, with the blue wire severed, there is an issue on the vehicle or trailer wiring, most likely a short.

I attached an FAQ on troubleshooting brake controller installs for you to check out also.

expert reply by: Jameson C

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