The headlights are an important safety component of the 1997 GMC Yukon. The low beams illuminate the road without blinding oncoming drivers and the high beams allow for more light when the roads are empty. Unfortunately, switching to the high beams turns off the low beams -- and vice versa. Thankfully, there is a simple modification you can perform to keep both the high beams and low beams on whenever you switch to the high beams. This will allow for even more illumination in darker conditions.
Turn off the Yukon's engine and remove the keys from the ignition. Locate the fuse block under the rear seat.
Remove the cover from the fuse block order to access the body control module, or BCM.
Remove the cover from the BCM. This will reveal all the pins and connectors. The low beam harness has a yellow and orange wire. The high beam has a purple and orange wire.
Using some wire, connect pin 85 to the purple high beam wire. Connect pin 86 to the high beam orange wire. Connect pin 30 to the ground cable. Connect pin 87 to the yellow from the low beam harness. Test the headlights to make sure they work.
Place the cover back on the BCM and fuse block.
