Headlights don't work - sometimes

[JamesWalker]

2019 GMC Sierra 1500 Denali - Headlights will not turn on with AUTO mode. Will not turn on with manual switch either. Pull stalk and blue light comes on dash, but no headlights. Push button on stalk and A does not appear. OBD scan indicated occasional miscommunication between transmission and BCM. Front camera recently wasn't working, came to life after OBD scan.

 

HOWEVER, HEADLIGHTS WILL ALL SHINE BRIGHTLY AFTER PARKING AND LOCKING TRUCK for the delay shutoff. So, its not no bulbs, fuses or relays.

 

What is wrong? Where to look?

[BIGDOGx]

 

4 hours ago, JamesWalker said:

2019 GMC Sierra 1500 Denali - Headlights will not turn on with AUTO mode. Will not turn on with manual switch either. Pull stalk and blue light comes on dash, but no headlights. Push button on stalk and A does not appear. OBD scan indicated occasional miscommunication between transmission and BCM. Front camera recently wasn't working, came to life after OBD scan.

 

HOWEVER, HEADLIGHTS WILL ALL SHINE BRIGHTLY AFTER PARKING AND LOCKING TRUCK for the delay shutoff. So, its not no bulbs, fuses or relays.

 

What is wrong? Where to look?

Perhaps whatever sensor that is used to determine how dark it is. I think in my older k series it was that little round thing center dash. I think it is called the ambient sensor control or something like that.

 

 

Edited August 15, 2025 by BIGDOGx

[Silverado4x4]

4 hours ago, JamesWalker said:

2019 GMC Sierra 1500 Denali - Headlights will not turn on with AUTO mode. Will not turn on with manual switch either. Pull stalk and blue light comes on dash, but no headlights. Push button on stalk and A does not appear. OBD scan indicated occasional miscommunication between transmission and BCM. Front camera recently wasn't working, came to life after OBD scan.

 

HOWEVER, HEADLIGHTS WILL ALL SHINE BRIGHTLY AFTER PARKING AND LOCKING TRUCK for the delay shutoff. So, its not no bulbs, fuses or relays.

 

What is wrong? Where to look?

That's a strange one, for the hell of it I  would disconnect the negative battery cable from the battery for about 15min to reset the computer and see what happens then I look into replacing the headlight switch on the dash. Probably around 50 bucks 

Edited August 15, 2025 by Silverado4x4

[GETGONE]

On 8/15/2025 at 1:32 PM, BIGDOGx said:

 

Perhaps whatever sensor that is used to determine how dark it is. I think in my older k series it was that little round thing center dash. I think it is called the ambient sensor control or something like that.

 

 

 

On the T1's it's a square block that looks like a GPS antenna on the center of the dash. Make sure something's not covering it or got spilled on it since it's directly behind the little storage recess on the dash.