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2004 gmc envoy_sle
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Discussion Starter · #1 ·
I have an 04 Envoy. The headlamps will work when I turn them on, but today they stopped working in automatic mode. Any ideas? Thanks!
 

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2004 gmc
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Do they come on dimmed during the daytime (DRL) mode? Any difference between high and low beams?

Could be a failure of the BCM (body control module) that controls the logic, or more likely, a failure in the ambient light sensor on the front of the dashboard.

Put a magazine over the sensor for a minute and see if that might force the headlights to come on.
 

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2004 gmc envoy_sle
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Discussion Starter · #3 ·
The lights are not coming on at all in DRL mode. No difference with high/low beam. While in DRL mode I put a magazine over the sensor and the lights came on. When I removed the magazine, the lights went off.

You think the light sensor is not working properly?
 

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Your sensor sounds OK, then. Just a difference in terms. When you say automatic mode, we usually think that means full-on night-time mode turned on by the sensor thinking it's dark out.

OK, it looks like your only failure is DRL mode.

Try interchanging these two black relays under the hood fuse block. One controls the DRL function, and the other is the electric fan clutch. Make sure to keep the orientation right:

 

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Discussion Starter · #5 ·
I swapped the relays as you indicated (great pic btw!). Unfortunately, no luck. The lights still will not come on in DRL mode unless I cover the light sensor.
 

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I photoshopped that pic for another member with a similar problem. Yours is different now. Sigh....

That the low beams work in night-time mode means the relay is OK and so are the downstream fuses, one for each lamp.

What's next in line is the BCM, an expensive computer component near the rear seat fuse block, and the main headlight switch. There's a DRL disable position on the switch, to the extreme left, but even if you did that accidentally, it should reset itself on the next ignition cycle.

For the heck of it, can you try that DRL disable function, and see if the DRL disable lamp on the headlight switch illuminates?

Any chance your parking brake is slightly on, which also disables the DRLs? I just tried the parking brake on my 2004 just now, and having it on did NOT disable the DRLs, so they must have changed the software and didn't tell the manual writers.

My shop manual says the DRLs are also disabled if the transmission is in the PARK position, and I confirmed that's true.

Any chance you've been doing these tests in PARK only and not while in gear?
 

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2004 gmc envoy_sle
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Discussion Starter · #7 ·
This is the part of the thread where I want to go crawl under a rock in embarrassment. I was in park. When I took it out of park it worked. Well...fwiw...I have learned something new today. It is much appreciated. I am sorry for wasting any of your time!
 

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.....I have learned something new today....
It's my 57th birthday today. Looking stuff up for your issues and a few others today helped ME learn five new things. So it's entirely a non-wasted day, and don't worry about anything.

Welcome to trailvoy, and good luck with your blower resistor problem.
 

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2002 gmc envoy_sle
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Well, give yourself five of these and call it a lesson learned!
:duh: :duh: :duh: :duh: :duh:
 
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