How to Diagnose Toyota Pickup Tail Light Assembly Problems
The Toyota pickup tail light assembly is as uncomplicated as any light with an on and off switch: brake lights will come on when you press the brake pedal; the lights will go off when the pedal is released. Hazard, turn signal lights, and reverse lights work on the same principle. If something goes wrong though, information below will help you save a lot of time, trouble, and money:
Hazard lights don't work, but turn signals do
The problem is obviously neither the bulbs nor the turn signal switch. First, check if the fuse is busted. If the fuse is good, check if the hazard switch is creating a proper ground. Usually you can fix the ground by spraying WD40. Or, if you find this process messy, an electrical cleaner is a better alternative.
The brake lights don't come on
Check if the third light comes on when you depress the brake pedal. If the third light doesn't come on, the problem may be a bad fuse, brake light switch or unplugged harness. Check the emergency flashers if it turns on. Flashers will not come on if the problem is bad wiring the since they use the same wiring. If the flashers are working, check the fuse. Change the fuse if busted. Change the bulbs if the fuse and the wiring are okay.
No brake light on one side
Since the other brake light is working, the problem is likely the harness or the bulb. Check if the wiring is loose or if the bulb is busted. Repair the wiring as needed. Check the socket for corrosion and clean it if necessary. Test if the bulb is busted by using the bulb on the other headlight and test it to the side that's not working. If it comes on, the bad bulb has to be replaced.
The lights don't come on after changing the fuse
Check the fuse again. Most likely, the fuse is busted again because the electrical circuit is shorted to ground. This rarely happens, but when it does, you have to manually check the wiring. Refer to the car repair manual for the wiring schematic of the brake light circuit. Once you locate the problem, repair as needed and replace the busted fuse.