Four problems related to wiring have been reported for the 2003 GMC Sierra. The most recently reported issues are listed below.
Day time running light burned out. When I replaced it the bottom of the bulb was burned and the plastic wiring socket was partially melted and brittle around the bulb base. I changed the bulb and the light still works. However, I also had trouble with one of my two horns not working, but after replacing the burned out bulb, both horns worked. Wiring seems to be in series with horn(s) and burned out bulb disables horn.
Day time running light burned out. When I went to replace it (still the original bulb) the bottom of the bulb was burnt bad and the plastic wiring socket was starting to melt around the bulb base. I changed the bulb and the light still comes on. I thought I better check the headlights. Changed those bulbs but the wires look like they are blistering from over heating. Never did blow a fuse. Seems to me like wires are too small for the amps the lights draw, especially the daytime lights. No fire yet but seems like this could possibly set things up for a fire.
The contact complained about many defects with this vehicle. The speedometer continually had an inaccurate read out while driving. The dealership believed this failure could be related to the wiring harness. Since they were unable to duplicate the problem no repairs were done. Also, the vehicle stalled at various speeds without warning. While the stalling occurred the contact pressed hard on the brakes to elevate the stalling. He believed this was due to the power brakes. The vehicle stalled on occasion and would not immediately restart. The dealership made numerous attempts to correct this problem w and all attempts have been unsuccessful. This included replacing the fuel pump and electrical control module.
On may 31st, the rear end differential assembly exploded sending the pinon thru the housing and the rear axle caught on fire. The truck was in the shop (perry cheverolet, inc. , columbia, mo)until 6-9-03. When I arrived in bozeman, mt on 7-2-03 I was having problems with the wiring. There was a fire when I plugged the RV electrical plug into the truck's trailer plug. There was also a blown rear tail light bulb. In bozman, they replaced the complete wiring harness, the tow receptacle and 2 fuse kits. It was the opinion of the shop in bozeman (j. C. Billion, GMC) that the wiring damage was part of the original fire and differential assembly damage. Although GMC paid for my out of pocket expenses and for the waranty work, I am left to wonder what will happen next and just how safe am I going to be in this truck? I selected a truck bigger than what I needed at the current time, thinking that if I replaced my travel trailer in the future, I would not have to trade trucks also.