The 7, 8 or 11 button Multi Information Display below the heater or the 18 Button on board computer in the same location.
However, as you ask I would assume you do not have one. The reason for asking is check control cars have both brake light circuits wired separately from the switch backwards.
Is this a new problem or did you but they car with this as a pre-existing problem?
Then your check control should be displaying "Check Brake Light" or "Check Brake Circuit" Is it?
On check control cars the brake light switch on the pedal is notorious for failing. However, you should verify if you have power on the correct pin in the tail light plug and if not that there is power at the correct pin on the brake light switch when the pedal is pressed, and none when not pressed.