Four problems related to headlight switch have been reported for the 2007 GMC Envoy. The most recently reported issues are listed below.
The daytime running lights (drl) and the low beam headlights do not light even when the dashboard light switch is placed in the �headlight� on position. Troubleshooting revealed that this failure was caused by the body control module (bcm) located beneath the rear seat. A digital logic signal from this module, based on sensor inputs from the ambient light sensor, parking brake and windshield wipers, is provided to the under-hood electronic relay that activates the headlights. There are three possible signal outputs from the bcm. . . A logic low (lights off), a logic high (low beams full on) or a pulse width modulated signal to create the dimmer drl low beam intensity. If the bcm fails, the low beam headlights will not turn on. There is no affirmative input to the electronic relay from the light switch, not routed through the bcm, to activate the low beam headlamps. This is a major safety issue. When the bcm fails at night, the driver has no low beam headlamps. The only lights available are the fog lamps or the high beam lamps, but only after setting the dashboard light switch to the headlamp position. Headlamps are a necessity, not a optional feature. Their operation should not rely on an electronic sub-system whose failure mode prevents the low beam headlights from working. This system was designed the �easy� way without regards to vehicle safety. . . Namely that when the dashboard light switch is in the on position, the headlights are enabled by a signal directly from that switch. Without an affirmative enabling signal from the manual dashboard light switch, the system and vehicle operator is at the mercy of the bcm, which could fail at night or on the weekend (when a repair shop is unavailable) rendering the vehicle dangerous or un-driveable.
I'm having a problem with my headlights going off while I'm driving down the road. It seems to happen while the lights are in automatic mode and when I try to switch them on manually after it happens it takes a few minutes for them to respond. This has happened on numerous occasions. And others that I know with the same model vehicles are having the same problem.
While driving at night on a city street the interior/dashboard lights, radio and headlights shut off. The car was able to drive off the main road and after turning the headlight switch to the left and right several times the lights came back on. The cause of the problem is unknown. After several weeks I have not seen the problem reoccur and have not been able to recreate it. Cause of the problem is unknown. I contacted the gm dealership and they said that nothing like this had been reported to them on other vehicles, and to bring the car in if the problem reoccurs. +.
I got in to my car the other night at around 7pm put it in drive and the headlights would come on so I tried the switch to turn them on manually and that didn't work, so I turn my car off and started it again and they still wouldn't work my hi-beams worked but my low beams and my daytime running lights don't work anymore. I have replace the bulbs and the relay switch and still nothing. So now I have to drive with my hi-beams on which is not good I got pulled over for driving with them on. I called the dealership where I purchased it and they said that my powertrain warranty doesn't cover for them to look at it & they want $75/hr just to look at it I can't afford that.