First thing to check is if you are getting power to the rear tail light. Pull it open and with the lights on check for power at pin one (white/yellow stripe wire) in the connector. If you have power check the connector inside to see if the actual connector is loose on the pin on the circuit board.
Since all of those lights share a ground it is likely to be a power feed issue. From the park lamp relay. If it is turning on (should be if all the other park/tail lights work) then it is in the wiring to the left tail light, either the pin is loose or the wire is bad.
Now for the brake lights, the only common items between the headlights and the brake lights (if nobody has played with the wiring) are the forward control module and the IPM.
To see if it may be the problem, check at the brake light switch for power on one terminal and not the other. Then turn on the lights. If the power goes away now it is the IPM or forward control module,
Below are the wiring schematics to give you the wire colors to test.
Images (Click to enlarge)
Wednesday, March 17th, 2021 AT 6:22 PM