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Ask Gm Tech (Cam) Your Own Question
Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 29427
Experience:  GM Grand Master Technician 2007. 14 year experience.
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2007 GMC Envoy low beam headlights went out last night. I

Customer Question

2007 GMC Envoy low beam headlights went out last night. I was unable to turn them back on regardless of the manual switch position. Eventually they came back on. Today the automatic light feature stays on and will not shut off unless I turn the manual knob to the off position.
JA: Have you checked the fuses? Have you checked the bulbs?
Customer: I replaced the HDM relay today, since that solution is the most frequent one I find. Bulbs are fine.
JA: Are you fixing your Envoy yourself? What have you tried so far?
Customer: CHanged out HDM in position 46 in the fuse panel
JA: Anything else you want the mechanic to know before I connect you?
Customer: No that's it.
Submitted: 26 days ago.
Category: GMC
Customer: replied 26 days ago.
2007 GMC Envoy low beam headlights went out last night. I was unable to turn them back on regardless of the manual switch position. Eventually they came back on. - What I meant was they came back on with the switch it the automatic position, no interaction from me.
Expert:  Gm Tech (Cam) replied 26 days ago.

Hi there, I am Cam.
With yourEnvoy, your right to look at the HDM, usually its the issue. As long as your are certain you replaced the HDM and not the driver module for the fan as they are back to back. IF so then let me ask, do the high beams operate properly when cycling them on and off, and when you go to low, the low beams are simply out?

Customer: replied 26 days ago.
high beams work. Marker, tail, and fog lights all worked normally. Confirmed new part in position 46 not 45 (fan). Daytime running lights work when manual headlamp switch is in off position. That was not the case last night.
Expert:  Gm Tech (Cam) replied 26 days ago.

Ok, are you able to do some testing?

Customer: replied 26 days ago.
Kind of. I'm at work. What did you want me to try?
Expert:  Gm Tech (Cam) replied 26 days ago.

I have the diagnostic for this issue. Its attached. If you can follow through it, you should find the issue. I am thinking a wiring issue, switch issue or BCM issue.
Also the wiring is included.

Expert:  Gm Tech (Cam) replied 26 days ago.

the wiring.

Customer: replied 26 days ago.
OK. I'll try these when I get a chance. Thank you. What the next step here if these don't resolve the problem?
Expert:  Gm Tech (Cam) replied 26 days ago.

Honestly those should. The only thing else I can add is to manually ground the 2 wires, one at a time at the multifunction switch to see if the headlight dimmer switch is bad.

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