I replaced both upper tail light assemblies a couple years ago with new units from AB. But for the past several months Ive been having issues with the brake lights always staying on. Replaced the bulbs, checked the wire harness for corrosion and replaced the brake light switch; nada no results.

The symptoms:
Driver side brake light always fully illuminated and unresponsive to brake pedal. Only way to turn off brake light would be to turn off the lights or turn truck off.

Solution: Replace the wiring harness inside the upper tail light assembly. I found this out when I removed the driver side tail light assembly and plugged in a spare passenger side tail light assembly. When I turned the lights on the tail light worked as it should and brake light was not illuminated. I then tested the brake light by fixing a rod between driver seat and brake pedal, then went back to inspect the light and BOOM it was illuminated as it should be. So this told me that neither the brake light switch now the vehicle wiring harness that connects to the upper tail light assembly was faulty. So I swapped out the tail light wiring from my spare unit and ALL IS WELL. Everything in working order.

Brake pedal pressed
Both brake lights illuminated with brake pedal pressed.
Brake pedal released, driver side brake light still illuminated
No signs of water contamination
No signs of corrosion or damaged wiring

Good bulb

Clean contacts
vehicle harness looks good
Testing a spare upper tail light assembly. Lights switched on and brake pedal released. Both brake lights are off as they should be
Brake pedal pressed and both brake lights illuminated as they should be. So vehicle harness and brake light switch are functional and the spare tail light wiring harness can be used.
Swapped over the tail light wiring from spare to my driver side tail light assembly.
Everything in working order.
Everything in working order.

 

Your high-level brake light isn't working though.

 

And, aren't the lower bumper lights suppose to illuminate? Not sure myself, will have to checkout our 03.

Brian.

 

Lower bumper lights are fog lights, at least on my '99. They come on with a separate switch.