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2005 GMC Yukon XL SLT Rear Wheel Drive, 5.3 liter V8.
I’m having strange issues with the computer controlled auto headlamp feature. If I start the engine with the auto headlamp light sensor on the dash in the sun the headlamps do not come on and the daytime running lamps come on when the transmission is in drive. This is normal and a desired function.
If the auto headlamp light sensor on the dash is in any kind of shade the headlamps come on and stay on even when the Yukon is driven down the road in bright sunlight. The daytime running lamps do not come on because the headlamps are on. This would be a normal function for the daytime running lamps.
The computer sometimes turns the headlamps off after a few miles, so that is OK I guess.This is the problem. The shade is gone quickly but the computer does not turn the headlamps off even though the sensor is now in lots of bright sunlight. I’m guessing the sensor needs to be replaced.
However; the other weird issue is when the computer turns on the headlamps and I manually turn off the headlamps the dash lamps stay in the “headlamps are on” mode. I have to adjust the brightness of the dash lamps to see the displays. No matter which way I turn the control and back to Auto the dash lamps stay dim.My headlamp manual controller has these settings:
Always in Auto
Can bump left to off and it springs back to Auto
One click right to parking lamps on
Two clicks right to Headlamps On
See attached Pic for controller design.Any input anyone may have on this is welcomed.
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Replies
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[quote=”bonrea” post=176085]2005 GMC Yukon XL SLT Rear Wheel Drive, 5.3 liter V8.
I’m having strange issues with the computer controlled auto headlamp feature. If I start the engine with the auto headlamp light sensor on the dash in the sun the headlamps do not come on and the daytime running lamps come on when the transmission is in drive. This is normal and a desired function.
If the auto headlamp light sensor on the dash is in any kind of shade the headlamps come on and stay on even when the Yukon is driven down the road in bright sunlight. The daytime running lamps do not come on because the headlamps are on. This would be a normal function for the daytime running lamps.
The computer sometimes turns the headlamps off after a few miles, so that is OK I guess.This is the problem. The shade is gone quickly but the computer does not turn the headlamps off even though the sensor is now in lots of bright sunlight. I’m guessing the sensor needs to be replaced.
However; the other weird issue is when the computer turns on the headlamps and I manually turn off the headlamps the dash lamps stay in the “headlamps are on” mode. I have to adjust the brightness of the dash lamps to see the displays. No matter which way I turn the control and back to Auto the dash lamps stay dim.My headlamp manual controller has these settings:
Always in Auto
Can bump left to off and it springs back to Auto
One click right to parking lamps on
Two clicks right to Headlamps On
See attached Pic for controller design.Any input anyone may have on this is welcomed.[/quote]
I believe your on the right track with the light sensor having a problem. As for the Light control
springing back to auto if you are in Canada or bought a Canada vehicle its a law there that the lights
can not be turned off. If not in Canada or vehicle then the control sounds like its having an issue. You should
be able to go to off.The Yukon was purchased in the USA however I believe it was assembled in Canada. The light control switch can only be turned to off then it springs back to auto. Only when the computer is being told that the outside light is bright or it is daylight do the dash lights remain dim.
I need a way to test the circuits to find the culprit in the devices. Hmmm…
Is there a video on how to replace the light sensor?Today, an absolutely gorgeous day here in NC, I pulled the dash apart and managed (with the help of my friend with small diameter arms) get the old Ambient Light Sensor out and the new one in. NOT ONLY did this truly solve the issues with the headlamps and the dash lamps BUT it did something strange.
I went earlier this week to seek out the correct Ambient Light Sensor part number in hopes of finding it online at a lower price. I resorted to the parts house because I kept finding conflicting information on the Web. Two to three different part numbers. Well… Which one to get? No clear answer. Off to the parts house I went.
The fine folks at the GMC Dealer parts house kept asking me all kinds of questions about the types of equipment on the Yukon. The usual Year, Model, Engine Size, etc.. Then he hit on one that made me go… Hmmm… So I had to ask. He wanted to know if the Yukon had the Automatic AC Control System. Well… “Yes it does but what does that have to do with it?” As it turns out, that models with the Automatic AC Control System the Ambient Light Sensor feeds the system light level info as part of the control of the cabin temperature you set on the little screen. WOW! “Why” I had to ask. He said that when there is really bright sunlight the cabin can become hotter much faster so it tells the AC system to increase the blower speed even though the temperature sensor says the air is at the correct temperature already. I NEVER found any information on that anywhere.
Well… Now that I have the Ambient Light Sensor replaced… He was absolutely correct. I have been having trouble with the Automatic AC Control System not changing the fan speed as needed but now… It is working perfectly again. Who would have thunk it?!?!
So this thread can be closed with the answer to my and hopefully other owners problems like mine.
[quote=”college man” post=176855]That was a technical happy ending. :)[/quote]
See the first paragraph of my post. It solved both problems and made me REALLY happy. I now have my Yukon in all aspects working like new. Just wish someone would offer me the new version price for it. Last I looked a replacement for my 2005 to a 2017 model is $80,000. WOW
And today I discovered you can option a 2017 Chrysler Pacifica minivan to over $51,000 with options and destination (before incentives and other discounts). And still no AWD until next model year. That’s why we all have older vehicles, and why we are here in ETCG-Land.
Glad to hear that you got it fixed. I had a similar issue with my 2001 Suburban. I don’t have the Auto Climate controls, but the Ambient light sensor was causing my lights to go haywire. I picked up a new sensor at the local Chevy dealership for under $20, swapped it out and all has been fine ever since.
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