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Question

my headlights turn off when I start the engine '03 Denali


Sent to Car Experts December 07, 2005 4:14 a.m.
Logically it could'nt be a fuse problem as the low-beams come on at un-lock. When I start the engine the lights go out and there's no response from the light switch. All that remains is the hi-beam mode or fog lights. I've never seen anything like this. It just started last night.. it's been cold recently! Is this a computer problem?

Optional Information:
2003 GMC Denali Vortec 6000

Already Tried:
Checked fuses and read owners manual. Local Dealer is an A-hole!
Customer (name blocked for privacy)
Status: Closed   Value: $20   
Answer
December 07, 2005 7:07 a.m. (2 hours and 53 minutes later) 		REPLIED Check Mark
Sounds like a multifunction switch problem possibly.I would assume you have operated the dimmer switch.There is a low beam relay but it should be good if the lights come on at unlock.That would also verify the fuse as you said and the BCM being able to control the low beams through the circuit.

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Reply to Davo/diablo666
Sent December 07, 2005 12:06 p.m. (4 hours and 59 minutes later)
The multi-function light switch appears to work, and like you said the relay also. The headlights (in auto mode) automatically stay on continuous. No, this is not related to the dimmer function. At start-up, the lights momentarily dim due to the amperage required by the starter, but stay on constant unless overridden by the multifunction switch. Realize that I am an electronic tech/trouble shooter with significant auto experience too. I just can't stand the dealer and the rip-off tactics, my warrantee just expired. Please look into the possibilities of a computer related problem (micro-processor). Thank you, and good day to ya. Mr. Smith.
Customer (name blocked for privacy)
Info Request
December 07, 2005 7:54 p.m. (7 hours and 48 minutes later)
How did you test the dimmer switch function?

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PictureDavo  -- Master technician -- 100% Positive Feedback on 1871 Car Accepts
ASE Master Technician/Advanced Automotive Diagnostic Technician
Reply
Sent December 07, 2005 8:06 p.m. (11 minutes and 55 seconds later)
When you pull back on the multi-function turn signal lever, the hi-beams activate but no lo-beam. Why would the automatic function of the headlights stop working? Again, the low-beams activate at 'unlock', but fails after ignition. Are we on the same page with this? I've owned this vehicle 2 1/2 yrs. and I'm quite familiar with its controls. Nothing has changed or been tampered with, I just noticed that last night the lights failed to return on after turning the ignition switch on. Please don't give up on me!
Customer (name blocked for privacy)
Answer
December 07, 2005 9:08 p.m. (1 hour and 1 minute later) 		REPLIED Check Mark
It could be the body control module have you checked for dimmer switch signal to the bcm?

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PictureDavo  -- Master technician -- 100% Positive Feedback on 1871 Car Accepts
ASE Master Technician/Advanced Automotive Diagnostic Technician
Reply to Davo/diablo666
Sent December 07, 2005 9:31 p.m. (23 minutes and 33 seconds later)
I didn't say that I was an auto tech. I'm experience as an electronic tech/trouble shooter and have automotive experience. How do I test for "dimmer switch" signal to the BCM without a diagnostic code reader? Please... I'm not trying to have a pissin' contest with anyone! The previous responses did not feel like they were listening to what I was saying. Now you're speaking auto technese and I would appreciate more layman terms. If you're telling me the BCM is the failure, then I will purchase and replace it. Can you convey why you believe this would solve my problem. Thank you for your time.
Customer (name blocked for privacy)
Answer
December 08, 2005 8:17 p.m. (22 hours and 45 minutes later) 		ACCEPTED Check Mark
Try this unplug the wiring at the multi function switch.Turn the headlight switch to on do the low beams come on yes or no?

__________________
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PictureDavo  -- Master technician -- 100% Positive Feedback on 1871 Car Accepts
ASE Master Technician/Advanced Automotive Diagnostic Technician

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