GMT800 DRL Ambient Sensor Questions - Lil’ Help Pls

[Scott in AZ]

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.

 

[Tonyrodz]

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

 

[Scott in AZ]

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

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.

 

[Fless]

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.

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

 

[Doubeleive]

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

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

 

[Rocket Man]

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.

How to: Take out Dash (nbs)

www.gmfullsize.com

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.

 

[Scott in AZ]

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.

 

[Tonyrodz]

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.

Make sure you get some adhesion promoter.

 

[Rocket Man]

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.

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

 

[JCODOHERTY]

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.

 

[JCODOHERTY]

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 will be checking the sensor's connector in the morning. I replaced the sensor and DRLs aren't switching on. The head lamps are on instead. Swapped relays and no change. If it isn't the relay or the sensor or the new sockets and new 4114LL bulbs it has to be the big diode under the dash?

 

[Doubeleive]

I will be checking the sensor's connector in the morning. I replaced the sensor and DRLs aren't switching on. The head lamps are on instead. Swapped relays and no change. If it isn't the relay or the sensor or the new sockets and new 4114LL bulbs it has to be the big diode under the dash?

have you tested the drl fuse?
there is no "big diode" that I know of anyway, there is a "sun sensor" which works as the daylight sensor and also works as a sensor for the hvac. make sure it is connected to the harness and twisted into its slot in the dash properly
sometimes they get worked loose and fall inside a bit or the harness can be disconnected.
the space under the dash (behind the radio) is pretty tight you need a flashlight to see in there, probably a little bit of foam in the way that can just be pushed down or taken out.

 

[JCODOHERTY]

have you tested the drl fuse?
there is no "big diode" that I know of anyway, there is a "sun sensor" which works as the daylight sensor and also works as a sensor for the hvac. make sure it is connected to the harness and twisted into its slot in the dash properly
sometimes they get worked loose and fall inside a bit or the harness can be disconnected.
the space under the dash (behind the radio) is pretty tight you need a flashlight to see in there, probably a little bit of foam in the way that can just be pushed down or taken out.

Thanks. Will check the connection again. Fuses all good. Maybe I'm thinking of a diode for something else. Relay seems good. Just replaced the ambient light sensor (original turned to dust). It is in the slot correctly. Will clean pigtail contact and check again. I did pull the dash cover out of the way to replace sensor. And then reinstalled late in the day. Can't see it with flashlight past the foam. Also checking again under steering wheel/above pedals to see if any other connections worked loose as well. Thanks again