We have a 2005 GMC Envoy that the Left, Right, and Third Brake Lights do not work when the pedal is pressed down. I have checked and replaced all fuses, bulbs, circuit boards, and the pedal switch. Still no brake lights. We do have this Envoy equipped with the trailer towing package. I even plugged my neighbors enclosed 24' car hauler to the Trailer Plug-in and guess what, we had brake lights on the trailer, just not the Envoy itself. So right now, unless we win the lottery or we buy a trailer to be pulled permanently by the Envoy, we only have ONE vehicle to drive. It's very lucky that I only live 8 miles from work and can drive the back roads. Course, she will be putting 40 miles one way on our Silverado every day. The running lights, turn signal lights, headlights, license plate light, and the back-up lights all work. Any Ideas?