Brighten Up Your Driving Experience With This Simple Upgrade Inside Your Fuse Box. Simply Install The Gm All Lights On Module To Allow Your High-Beams, Low-Beams And Fog Lamps To Simultaneously Illuminate The Road Ahead. Once Installed The Gm All Lights On Module Will Turn On The High-Beams, Low Beams And Fog Lamps When You Turn On Your High-Beams.Fitment Guide: 2003-2007 Classic 2500-3500 Silverado/Sierra Installation 1. Remove The Relays Labeled: Fog Lp, Hdlp-Low, Drl, Hdlp-Hi 2. Lay The Gm All Lights On Circuit Board In The Location Shown (See Product Images) 3. Reinstall The Four Relays Back Into Their Original Location.