1999 subaru impreza brake light not working but tail light works

Light bulbs require power and ground in order to work. The ground circuit for the left rear combination lamp is shared between the turn lamp, stop lamp and tail lamp. Because the tail light still works in that specific combination lamp, we know that the shared/common ground for that assembly is OK. The power circuit for both stop lamps (left and right) have the same origin; voltage flows from the STOP LP FUSE (15A) through the DBC RELAY (when the stop lamp switch is pressed) and then to each stop lamp via their respective circuit branches. Because the right stop lamp works, we know that the shared/common fuse, relay and switch are all OK. I'd suspect an open in the left stop lamp power supply branch and would recommending checking for voltage on the green & black wire at the left rear combination lamp assembly to confirm. Regarding the left lamp on the hatch, the wiring diagram indicates these are not stop lamps rather tail lamps only. I'd recommend installing a tail lamp bulb instead of a brake light bulb into that assembly as a first step. You can read more here: https://www.yourmechanic.com/article/how-to-replace-your-car-fuse-box-by-jessica-howe

Check your tail light fuse.

The first step is to verify that the tail light bulbs are not burned out. I Next step is check
a) if you get+12v on the bulb, and
b) check for poor grounds to rear light cluster.

There is a fuse for parking lights. If all this check out then trace the wiring harness under the carpet from the driver seat to the rear for rust/water damage.

check brake switch

Hi,
So, both sides are not working? Check for voltage @ the brake light bulb to see if you're getting power. Also, look in the fuses.

check out the online Subaru forums, too.

GL,
Td

Mr. Williams since you tried with fuse,bulbs and brake light switch with no success,why you do not try to check your circuit by using a tester and see whether you have any broken wire or bad earth?

first of all check and confirm whether in the fuse box separates the left from right side and see for blown fuse. or check for any disconnection on the rear light

50-60 psi is not enough. you want 130+

Replace the bulbs.
The bulbs will have two seperate elements in it which is why the brake light works.

Take the bulbs out and you will see the seperate elements.

Check for power at the lights. If there is power then it's probably a bad ground. If not then you need to start checking the wiring harness for breaks or loose connection. Good luck, Neil W.