Troubleshooting the brake lights on your GMC 1500 truck is fairly simple. The three most common problems with GMC 1500 brake lights are loose connections, burnt-out bulbs and broken fuses. All of these issues have simple solutions that only take a few minutes to fix. As brake lights are important for safely driving your GMC truck; they should be fixed as soon as you notice that they are malfunctioning.
Turn off your truck's engine and open the tailgate. Use a Phillips screwdriver to remove the two tail-lamp assembly screws near the tailgate latch. Pull out the tail-lamp assembly and lightly tug on all four electrical connectors to make sure they are securely plugged in. If the brake lights are still malfunctioning, there may be a problem with the bulb.
Press the release tab on the top two bulb sockets to remove them from the assembly. The top two bulbs are the stop lamp bulbs. Pull the old bulbs out from the sockets and place new bulbs into the sockets until they snap into place. GMC 1500 trucks use 3047 type bulbs for all tail-lamp lights. Snap the socket back into the tail-lamp assembly, making sure the release tab clicks into place over the socket. Reinstall the tail-lamp assembly and fasten the two tail-lamp assembly screws. A broken fuse may be the problem if the brake lights still do not work.
Open the driver's side door. The instrument panel fuse block is located on the driver's side edge of the instrument panel. Pull off the cover to access the fuse block. The fuse labeled "6" is the driver's side turn signal and stop-lamp fuse. The fuse labeled "8" is the passenger's side turn signal and stop-lamp fuse. If the metal rod inside either fuse is broken, the fuse has blown and needs to be replaced.
Grasp the broken fuse with your thumb and index finger and pull it out. Make sure to only use a 10-amp fuse as a replacement. Place the replacement fuse into the fuse block. Place the cover back onto the fuse block and close the driver's side door.
