If the brake light does not come on, check the fuse in the fuse box first.
If the fuse is good, check the brake light bulbs and replace if necessary.
If the bulbs are OK, then check the brake light switch. Above the brake pedal on the pedal unit is the brake light switch. When the brake pedal is depressed, the push pin extends from the switch. The switch contacts close and the brake lights come on.
Check the brake light switch. The switch is located in the footwell on the brake pedal support.
Turn on the ignition.
Bridge both contacts in the brake light switch plug with an auxiliary cable. If the brake lights now come on, the switch is faulty and needs to be replaced.