jeb

Nope. As I said above, I bought it brand new. Been a great truck.

Thanks. I'll find some time to see if I can trace it back. Looks like the BCM relay might need a look. But you'd think that since the DRL's do work for the lock/unlock, that'd be okay, too.

I just tested it. You are right that the DRL's do not come on when locking/unlocking in direct sunlight, but do in dark conditions. So there seems to be no question that the ambient light sensor is good. Fuse is good. Relay is good. Bulb and wiring are obviously good or they would not come on at all. Anyone know of wiring diagrams online for these trucks?

The DRL's and backup lights staying lit for 10 seconds after unlocking the truck happens in dark or light. I'm pretty sure they have always worked that way. The headlights are for sure not lit during daylight. I have no lights on at all right now in daylight. The headlights do come on automatically when it gets dusk/dark. The ambient light sensor seems to be funtioning as it should.

Sorry for the late reply, and thanks for the input. Dirt bike races have been consuming me of late, so not getting online as much. Yes, the auto headlight sensor does work as normal. Tested several times now as I'd read that was a possible cause. The signal lights also blink when I unlock/lock the truck. The DRL lamps come on with them, and stay lit for 10 or so seconds after the signal lights go out. Backup lights stay on solid like the DRL's for the same time duration.

Thanks for the reply. I did make sure the parking brake was not on. I've owned the truck since new, 86k on the clock. Always babyed it. And yes, the DRL's for sure used to work. I'm not sure how long they've been out.

I did some searching, but could not find what I need. I have an 04 GMC Yukon XL SLT (3/4 ton, 4x4, quadrasteer) and the DRL's just do not work anymore. I see lots of folks wanting to disable them, but I'd like to get mine working again. I pulled the socket on one side. The socket was a little blackened around the bulb, but still in good shape. Both bulb elements tested good with my Fluke meter (although it appears the socket can really only power one of the elements, so not sure why there's a 2 element bulb in there). I get no power to the socket terminals. Engine running, in drive, sunny day with the lights on or off. Nada. They do flash when I lock/unlock the truck, though. I changed the fuse and the relay for the DRL's, but it made no difference. If they didn't flash with the lock/unlock, I'd suspect a wire. But it's got me kind of mystified at this point. Any hints on what to look for would be appreciated. Is there an online wiring diagram for these trucks?