Daytime running lights won't turn on.
 

Im having issues with the running lights on my 2003 Tahoe. They will not come on while driving. They come on after locking the doors when the truck is off and that's it. It has the automatic headlights and they come on fine at night. Any ideas?

to clarify: for your model year, the dtrl bulbs are in the same housing as the signal lamp lens assembly....not the headlamp lens assembly

Yes they are.

so I assume the bulbs are good if the lights come on with the fob
-check the 10 amp drl fuse in the underhood fuse box
-check the drl relay in the underhood fuse box. have someone in the drivers seat...in daylight, engine running, ebrake off and trans in drive. when they make the shift from park to drive...you should feel and hear the drl relay click. if it does, the bcm is commanding the relay on. if it doesn't click, either the relay is bad...swap it ...or the wiring or bcm is bad...remove the relay and check for power and grd at the pins.

its a 4 pin relay....2 should have battery voltage at all times
one is a grd control to the bcm…..if you grd it the lights should come on.
the last wire is to the bulbs....if you power this pin the dtrl should come on...if they don't...you have a wiring problem to the bulb or bulb grd.

For sure check that the emergency brake is off, I spent a lot of time troubleshooting my nieces Suburban DRL's only to realize the brake was set!