GMT800 DRL Ambient Sensor Questions - Lil’ Help Pls

Help w Ambient Sunlight Sensor Replacement -

Hi from State48. I finished exterior and interior LED bulb swaps on my 2001 Yukon SLT 4WD. I also replaced the melted sockets for my Daytime Running Lights and when checking my work realized my low beams are always on. I’m pretty sure it’s the common problem of ambient light sensor on the dash has failed. I pulled the Audio Head Unit out and took a look and decided I can’t reach it that way. I’ve been in and around my dash and am patient enough for this but don’t want to crack the dash or lose the wire.

Does anyone have experience removing the dash top to access the sensor? Is this a good idea? Does anyone know which sensors I need (there are two different versions, 2-pin and 4 pin, I think)? Any help is appreciated.

@Rocket Man might be able to give you some pointers. He removed his upper dash on his 02 to repaint it.

Tonyrodz said:

@Rocket Man might be able to give you some pointers. He removed his upper dash on his 02 to repaint it.

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I would absolutely spraypaint it if anyone knows a good match color code for Pewter. I thought about painting black but not sure black would work on top. I think it would look good to paint the old dash top and the new monochrome Metra double-DIN dash front panel at same time. I’m sending back the pewter Metra front panel and swapping for black because not completely satisfied with the match.

Scott in AZ said:

Help w Ambient Sunlight Sensor Replacement -

Hi from State48. I finished exterior and interior LED bulb swaps on my 2001 Yukon SLT 4WD. I also replaced the melted sockets for my Daytime Running Lights and when checking my work realized my low beams are always on. I’m pretty sure it’s the common problem of ambient light sensor on the dash has failed. I pulled the Audio Head Unit out and took a look and decided I can’t reach it that way. I’ve been in and around my dash and am patient enough for this but don’t want to crack the dash or lose the wire.

Does anyone have experience removing the dash top to access the sensor? Is this a good idea? Does anyone know which sensors I need (there are two different versions, 2-pin and 4 pin, I think)? Any help is appreciated.

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@Doubeleive I thought had some tips for pulling these sensors out without too much dismantling.

Fless said:

@Doubeleive I thought had some tips for pulling these sensors out without too much dismantling.

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well a tech2 would be ideal I guess but you can get to the sensor from under the dash, I would confirm it is not working by covering it in daylight with a dark towel and see if the interior lighting goes dimmer or not. you might have to either use a flashlight and some long needle nose pliers or grab the sensor cap from above and try twisting it counter clockwise and it will come loose so you can remove it from below
sometimes the harness comes off the bottom and that could be a reason why it is not working, you should be able to see if it is attached with a flashlight.
if you can't get to it from below then you may have to cut the metal bracket that is behind the radio to have access, but I would try moving any wires or foam padding out of the way and try reaching in there it's tight but can be done with fingertips.
not sure if would be 2 wire or 4 wire you should be able to see it again with a flashlight

I’m almost positive you need to pull the dash top to get to those sensors. There’s a great write-up, link us in the tech section, here it is. It’s not hard at all.

I have painted mine, there’s a SEM Classic Coat color that’s pretty much identical. I can look that up tomorrow if you’d like.

Thanks everybody. I learned my way around the dash while installing new audio head unit with wiring for GPS antenna and microphone. Im convinced I can’t get to the ambient sensor thru the radio access but I’ve seen videos that indicate it’s possible. It looks too far back and too tight to be reliable project for me though. My hands are too big I guess. I’m going to pull the dash cover off, replace the ambient sensor and paint the dash. Will keep you posted.

Scott in AZ said:

Thanks everybody. I learned my way around the dash while installing new audio head unit with wiring for GPS antenna and microphone. Im convinced I can’t get to the ambient sensor thru the radio access but I’ve seen videos that indicate it’s possible. It looks too far back and too tight to be reliable project for me though. My hands are too big I guess. I’m going to pull the dash cover off, replace the ambient sensor and paint the dash. Will keep you posted.

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Make sure you get some adhesion promoter.

Scott in AZ said:

Thanks everybody. I learned my way around the dash while installing new audio head unit with wiring for GPS antenna and microphone. Im convinced I can’t get to the ambient sensor thru the radio access but I’ve seen videos that indicate it’s possible. It looks too far back and too tight to be reliable project for me though. My hands are too big I guess. I’m going to pull the dash cover off, replace the ambient sensor and paint the dash. Will keep you posted.

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That’s the exact color I used. Pretty much an exact match.

Did replacing the sensor fix the issue? I've got head lamps on, no DRLs. New sensor, new sockets, new 4114LL bulbs, new 3157 ambers and corner bulbs. Tried swapping relays, nothing. All other bulbs are as should be, except indicators now alternate blink with corner bulbs (I don't recall that in all the years I've owned the vehicle) and the head lamps are auto on in place of DRLs in daylight. I'm thinking it has to be the failing diode under the dash.