Check the easy one first, check the fuse.
Make sure the connection is clean also. Make sure you have power to/from the fuse. If you have no power to the fuse then maybe the turn lever housing is bad.
You may have a break somewhere in between the fuse and the light. Does the front work or just the back one not work?
If the brake light does work, you do have one power feed. You need to recheck that. You tester may not be working.
It's going to take some detective work. Start at the socket and work back through the harness inspecting and probing for power with your test light until you find the break.
Check the bulb- it is probably double filamented with smaller for brake light and larger for tailight
There are two filaments in the bulb that is used for taillights and brake lights. Make sure BOTH filaments are good before assuming that the bulb is not burned out. If, in fact, both filaments are good, next check the brake light switch. If it is good, check the turn signal switch that is in the steering column
from inside the trunk you can dislodge the tailight lenses.... the rest is simple
Check bulbs (double filamented small is for brake lights-large for tailight) Check fuse for stoplight Check stoplight switch
The tail light/brake light bulb has two filaments. If one of the filaments is broken, you will get either only tail lights, or brake lights. If a new bulb doesn't work, then you have a broken wire or bad connection in your plug-in.
because there is two filiments in the bulb one for brake and signal light and one for running light
Rarely, Brake liight bulbs generally have two filaments. Backups generally have one.
purple
you have to take out the rear tailight assembly from inside the trunk, there are 3 bolts, the then Slides towards the rear of the car, the whole tailight assembly does, you also have to take off the cover inside the trunk area. it's not hard.
Check the bulbs one of the 2 filaments may be burned out
Locate the 3 tailight screws securing each tailight on the inside of the trunk. Remove screws and replace bulbs. The entire procedure will take you about 5-10 minutes and that includes removal and replacement time. Jim janesville, Wisconsin
Check bulb they are double filamented smaller for brake light larger for tailight Check for a bad fuse Check the operation and adjustment of the stop light switch usually located at the upper end of the brake pedal under dash area