Lower brake lights on a 2003 GMC Yukon may fail due to common issues like bulb failure, blown fuses, or wiring problems. Address this with these straightforward DIY steps for a quick resolution.
Step 1: Inspect the Brake Light Bulbs
Access the rear light assembly by opening the tailgate and removing the cover panel. Check if the bulbs are burned out—signs include dark filament or discoloration. Replace any faulty bulbs with compatible replacements for your vehicle.
Step 2: Check and Replace Blown Fuses
Locate the fuse box under the dashboard or hood, referring to your owner's manual for the correct fuse. Identify the brake light fuse using the diagram. Test it with a multimeter or visually inspect for breaks. Replace if blown with an identical fuse rating.
Step 3: Test the Brake Light Switch
Find the brake pedal switch mounted near the top of the pedal. Depress the pedal while checking for audible clicks. If unresponsive, disconnect the switch connector and use a multimeter to test continuity. Replace the switch if defective.
Step 4: Examine Wiring Harnesses for Damage
Inspect the wiring leading to the rear lights. Look for frayed insulation, corrosion, or loose connections at sockets. Secure any loose wires with electrical tape and clean corroded terminals with a wire brush.
Step 5: Verify the Ground Connection
Locate the ground wire near the tail light assembly—it usually attaches to the vehicle frame. Remove bolts to expose the connection point. Clean corroded surfaces with sandpaper to ensure a solid, rust-free ground bond.