Does it have a door ajar light? If so is it functioning properly? If not try: spraying door latches liberally with WD-40, operate door a few times then spray with a good silicone spray. Although it sounds strange this has worked for me many times in solving the problem of dash lights coming onm with application of brake pedal
The bulb could be 'blown'. Remove the working bulb from the other light and try it in the socket of the one that isn't working.
Vehicle has been poorly serviced and maintained. Brakes should be inspected every service.
If all are out then its either the fuse (under the hood) or the switch (on the pedal assembly). If its just 1 side check the bulb.
Possible worn out brakes
Maby short in harness along rocker panels or on trunk......take trim loose turn on dash and tail lights and start jiggling harness wires. Moisture can cause problems like this as well.....
you might have a vacuum leak in your intake manifold
every vehicle must have brake lights to indicate that the vehicle is stopping. with no brake lights the vehicle can cause a rear end collision.
You need to have the abs checked for codes. Then you can diagnose cause.
vacaum leak or bad throttle position sensor. gm Jim
The most common cause is a broken or corroded ground wire.
Check around brake pedal for something rubbing. If OK, I'd look into the master cylinder.
There are 2 filiments in those bulbs. One for tails/turn and the other for brake lights. Try replacing one bulb first. I think there are two offest tits on the shaft of those bulbs. Be sure you insert it correctly into the socket. For that matter check to see if they are in correctly now.