Daytime running lights

Hi, my father has a 1999 GMC Safari, 4.2 litre, 2 wheel drive. His daytime running lights are not working, looking at the wiring diagram, I figure that it is probably the DRL relay or the DRL module (the fuses are fine). I just need to find them so I can check them with my multimeter. Does anyone know where they are? I had a quick look at it the other night, but I was unable to find the relay (I don't think that it is in the relay box under the hood). Any help would be much appreciated. Thanks.

The DRL relay is located in the under-dash cct breaker panel. See the owners manual - it shows you the exact location.

Also there's a DRL switch on the parking brake, so the lights don't work when the parking brake is in use.( at least on my '97) Maybe check that switch too.

Before you go to too much trouble, make sure the high beam bulbs work when you turn the headlights on manually. Could be all you need is two bulbs. Always remember the KISS...keep it simple stupid ;)