So , when you step on the brake pedal , the outer lights do not come on , but the parking lights work? have you checked along the harness in tailgate area for damage? Any work recently in the back , that something might have come unplugged?...... Just some thoughts of more to check........ain't it fun?
SO, YOU HAVE TO CHECK IF THERE IS POWER TO THE BRAKE LIGHT BULBS...IF THERE IS...YOUR PROBLEM IS THE SOCKETS OR BULBS...IF NO POWER, YOU HAVE TO CHECK OUT YOUR WIRING OR IF THE SWITCH IS ACTUALLY WORKING.
I had this same problem and now my car has gone crazy. It won't shut off when you remove the key from the switch, the transmission was acting crazy, the brakes froze up, pushing the gas pedal resulted in nothing happening, the fuse box gets hot and the mechanics cannot figure out what is wrong with the car. It throws no bad codes and the diagnostics came with nothing. Did you get your car fixed or did it go bonkers like mine???