I have a 2002 Silverado LS and the driver side tail light only lights up when I press the brake and I know its not the bulb cause its a new bulb and uses the same bulb for running light and braking light. But only the braking light will work. Does anyone know what the problem is?
There is a lot in this circuit ranging from the park lamp fuse(s), park lamp relay, body computer, a junction block at the rear of the truck and grounds to the circuit.
I would first check for current at the rear lamp assembly with a test light and work your way to the front of the truck so you can find where the power is lost in the circuit.
Remove the lamp assembly and remove the plug socket and see if you have current (voltage) to the wires for the park lamps. If you do and the lights don't light the problem could be in the internal circuitry of the lamp socket and may have to be replaced.
The PARK LPS 30 A fuse in the engine wiring harness junction block supplies battery positive voltage to both the park lamp relay switch contacts and the park lamp coil circuit. The Body Control Module (BCM ) provides a ground or control circuit to the park lamp relay coil circuit. When the park lamps are turned on the BCM energizes the park lamp relay. Current flow is from the park lamp relay to the FR PRK (Front park lights) 10 AMP fuse, RR PRK (right rear) 10 AMP fuse, LR (left rear) PRK 10 AMP fuse, and the TRL PRK 15 A fuse, and to their respective park and marker lamps.
The rear park and marker lamps are grounded at G401.
The body control module (BCM) provides a ground or control circuit to the park lamp relay coil circuit.
So check the fuses first and if they check out ok then check for current at the tail light relay for the rear lights. I have a feeling it could possibly be the fuse for the left side tail light. Let us know, if not we can go on from there.
Check for condensation and or corrosion inside the tail lights and also check the light socket for corrosion.
Remember there may be a junction block under the truck, this can get corrosion and cause this problem. This would be on the light blue wire in the junction block.
Try these suggestions and get back to me with your results.