[rhandwor]

My 2000 silverado has a plug within 18 inchs of the trailer brake control near the brake pedal unplug the connection and check. If this fixes the problem you know what to check. Just follow the wires from the controller they go to this plug.
A brake lite switch is near the brake pedal also. Then check the reverse switch.
The manufacturers put this plug in to prevent people cutting into wires with improper connections.
If you didn't use the plug locate it and buy a proper connector. Most trailer companies,U-haul and Northern supply sell the plugs and tell you what wires to hook to it.