Location of fuse for trailer plug on 2004 gmc hd 2500? Location of fuse for trailer plug on 2004 gmc hd 2500? The labeling of each fuse is on the inside of the fuse box cover. The power window fuse location can be found by looking at the diagram. GMC Sierra mk1 (2003 - 2004) - fuse box diagram - Auto Genius Dec 28, 2016GMC Sierra mk1 (2003 – 2004) – fuse box diagram. Year of production: 2003, 2004. Instrument Panel Fuse Block. The fuse block access door is on the driver’s side edge of the instrument panel.