[Whyman]

Not sure exactly what vehicle you have, try putting details in your signature so you only have to do it once.

Any way on mine they are wired in series with the orange marker lights in the headlight unit. Have these failed?

If yes the replace the bulbs in the marker lights and your DRLs might work.

Incidentally what appear to be DRLs on my XC60 are not bright enough and are just sidelights.