GMC Repair: 02 Yukon Daytime Running Lights, daytime running lights, light functions

Question
Just bought an 02 Yukon SLT and the daytime running lights are not working.  I tried replacing the fuse (even though it didn't look blown) and they still don't work.  I am guessing the light sensor works because the automatic headlights come on while I am in the garage BUT only after releasing the parking brake.  Of the things I am capable of reparing, I am guessing it is the relay or the bulbs.  Is it likely that both bulbs are out at the same time?  Is the relay replacable? Is there a way to tell which of these two is the culprit is without actually replacing the items?  Could it be something else?  All of the other light functions seem to work.

Answer
Hi
It is VERY likely that both bulbs AND the sockets they go into are burned.
It is a VERY COMMON problem on these vehicles.
If you go to the dealership, they will sell you a new designed bulb for the DRL's.
If you decide to replace the sockets also, it is a pretty easy, straight forward job, just cutting the wires and splicing in new sockets.
Just advise from experience.
Hope this helps
Paul