I installed a trailer brake controller in my 2003 GMC Sierra 1500HD that has factory installed tow package. The manual button on the controller will apply the trailer brakes but applying the brake pedal does not activate the trailer brakes. Without the trailer attached, pushing the brake pedal lights the left and right brake lights but not the high center light. Pushing the manual switch on the controller will light the center light but not the left or right brake light. What should I do?
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I found the problem. It was a burnt out fuse for the CHMSL.
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