Three problems related to brake light on have been reported for the 2004 GMC Envoy. The most recently reported issues are listed below.
My dash panel gauges began failing one by one. My headlights will sometimes not come on after starting the car with the headlight switch on auto. A flick of the headlight switch in and off, does not make the headlights come on. Sometimes they come on after driving around, and then will go off without touching the switch. Now, my side brakelights will not operate correctly when the brake pedal is pressed. Only the third brake light illuminates.
Transmission not shifting correctly, abs light, brake light, emergency brake light, 4-wd drive light, heat/ac crusie control not working. Found pi report, ignition switch replaced, fixed problem.
When contact comes to a yield sign transmission jerks before going into gear. Later he was told this was a brake problem. When approaching a hill/downhill and applying brakes they lock and car slides. Dozens of times check brake, service 4 wheel drive lights have come on. Contact has taken vehicle to dealer over 12 times since it has been purchased. Due service lights, brakes and transmission. Consistently told by dealer that nothing is wrong. But dealer aknowledges check brake lights have come on. Dealer states that if computer diagnostic does not produce an error code, then there is nothing they can do.