What about the emergency flashers and turn signals? Same or different bulbs?

Have a friend watch the tail lights or back up to a window so you can see a
reflection. Step on the brakes and wiggle the turn signal lever. See if one
or both come on.

If it was a ground problem I think it would be more likely to loose just one
side. Do you have a wiring diagram?

Al

Remove the bulb from the socket and use a test light to see if you have
power to the socket when you press the brake.  If you do then it's most
likely a bad ground and check these two items:

1.  Find the black ground wire from the wiring harness out of the light
assembly itself, tap into it and connect it to a grounding point nearby.
See if that works.

2.  Hook up a trailer and see if you have proper brakes lights on the
trailer.  If you don't have a trailer, use a test light to see if you have
power to the proper lead inside the connector.  If you have a trailer
connector spliced into the lines then check to see if the splice to the
ground wire has actually cut the wire (an occasional occurance when using
the blue crimp style clamp splices).  If you have a trailer connector wired
in on a T then remove it and reconnect the original ends and see if that
works.

If you don't have power to the bulb socket but the fuse is OK then it could
be a bad brake light switch under the dash.

Good luck - Jonathan

This can be the multifunction switch in the steering column which has the
red hazard button on top.  It is possible to push this hazard switch to the
left or right and have the left and right brake light operate when the brake
pedal is depressed.

Good luck because replacement is expensive and challenging.

Charlie