DRL not working on 99 Yukon

My 99 Yukon's DRLs aren't working. Checked the fuses, and bulbs. My brother has the same truck and we were double checking yesterday with his. My headlights work on dim, but on high, the outer bulbs in the assembly goes out, and in daylight there are no DRLs. Parking brake is not set or hung up to keep them off. Is there a relay or something to check? Can't find one. Where would it be located?

Thanks, Blondie

I dont know whats up with your DRL's, but as far as the quad headlamps, gm has a relay that only allows the high beams to work separately from the low beam bulbs, this can be over ridden, but I dont recommend it. Youre risking overheating the wiring harness. Good luck with the DRL's Mike

I dont know whats up with your DRL's, but as far as the quad headlamps, gm has a relay that only allows the high beams to work separately from the low beam bulbs, this can be over ridden, but I dont recommend it. Youre risking overheating the wiring harness. Good luck with the DRL's Mike
I have the same problem on mine also fog lights will not work, when automatic headlights come on , the instrument lights do not , have to use manual switch for inst lights.

Hi Blondie,
I am not sure about this, is the DRL function done by running the High Beams at a reduced voltage, or are there separate DRL lamps under the headlights?
Do you have the old body style with 4 rectangular headlights?
Take care, Eggert :bananasmi

I have the same problem on mine also fog lights will not work, when automatic headlights come on , the instrument lights do not , have to use manual switch for inst lights.
On 96 models there is a module and a diode under the steering wheel area. It was the diode on mine.