My DRLs are designed to come on ONLY when the engine is running, the transmission is in a forward gear, and the parking brake is off.
That said, my DRLs often do not come on unless I turn the headlights on and then back off. I can tell whether or not they are on from the cockpit if I turn on the fog lights and check the monitor light that tells me the fogs are on. The headlights have to be fully on or DRLs have to be on before the fog lights will come on.
If you have DRLs, you will have a small DRL module somewhere. Mine is a rectangle box that looks much like a turn signal flasher. It says "DRL" on it, which makes it easy in my case! My items like that are together in a basement storage compartment with a 12v breaker/fuse panel. In my experience, many gas rigs have the flasher modules, etc loose under the dash.
Paul (KE5LXU) ...was fulltimin', now parttimin'
'03 Winnebago UA 40e / '17 Jeep Grand Cherokee toad