My 1991 Olds Cutlass Ciera had that problem and it was corrected by replacing the turn signal switch. Troubleshooting with the factory service manual pinpointed the problem. Paul S
Bad bulbs or brake light switch.
Assuming you have checked the bulbs, check the brake light switch.
Check wiring for 12v also the brake switch on the brake pedal.
check that you have double filament bulbs in tail lights
Did you check the switch on the brake pedal assembly?
more than likely one of ur bulbs are out like blinker bulbs in front or rearor sometimes a brake light its happen to me
Have you tried brake light switch located on brake pedal or in that area?
Working brake lights are important for safety reasons while driving. It is important to check all of the wiring, if the brake lights are not working and the fuses and bulbs have been checked.
Have you checked the bulbs themselves? The directional signal should be the same element as the brake light. Check to see if you rear directional signals.
Likely to be the brake light switch on the pedal at fault if the bulbs and fuses are good and other lights work ok.
Check the brake light switch it should be connected to the brake pedal somewhere.
If you're positive it's not the bulbs (you know this because you checked them with a meter or tested the outlet with a test light maybe) or switch, check it out for a bad ground.