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Troubleshooting Brake Controller not Working on 2006 GMC Sierra  


I have a 2006 GMC that I use for testing trailers,until just recently. I no longer happier to the controler when the brakes are applied. The controler is pluged into the junction block. I have Mitchel repair program but have been unable to find the wiring diagram that applies to it. Ive checked all the fuses that I know of but must be missing something.


Expert Reply:

There are a number of troubleshooting steps you can undertake in order to try and determine what the issue is with the brake controller on your 2006 GMC Sierra

To test the brake controller itself, sever the blue wire a couple inches from the back of your controller. Then use a circuit tester such as # PTW2979 to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override; if it shows power at idle then there is an issue with the controller and it will need to be replaced.

If the controller tests fine, reconnect the blue wire and move on to the truck side trailer connector. Often, corrosion or dirt may be the cause of a short in a trailer connector. Check the plug to see if there is any type of corrosion built up that may be hampering its functionality.

You will also want to test the brake output pin on the 7-way socket; it should only show power with the manual override. If it shows power any other time then there is a short somewhere between the connector and the brake controller you will need to find.

It is possible the issue is on the black power wire so you may need to simply sever that wire and run a new one via a circuit breaker with # 10-1-1 from the controller to the battery if the issue is you are not getting power.

I have attached some help articles on testing and troubleshooting brake controllers for you to check out as well, which I highly recommend reading.

expert reply by:
Kyle S

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