It is one big peice that must be removed.
If you open the trunk, look on the inside of the lid behind the license plate, and you will find a few nuts that once removed, will allow you to remove the entire rear facia panel that the license plate bolts to and which houses the "Pontiac" lights.
Check the bulbs, check the fuse then check the switch.
check your fuses first, then check your bulbs and then your relay.
Probably the wrong bulbs or the brake lights are getting stuck "on". Or maybe a combination of the two. Check that you have the right bulbs and check to make sure something isn't keeping the brake lights on. FriPilot
To replace the brake light on a 2000 Pontiac Montana open the trunk to reveal the housing units. Find the lights and pull the bulbs out. Replace the units.
I'm guessing that all of the light bulbs have been checked and are good. It's possible that you need to replace the flasher.
I can't be 100 % sure as I'm not real familiar with your model, but my earlier Sunfire's bulbs are accessed from inside the trunk, You'll have to pull the carpet away from the body, then twist out the bulb holders.
in the rear facia, under the trunk lid there is 9 bolts holding the facia on. You must remove the nuts and pull the facia out and right above the license is the two bulbs 194. replace the bulbs and put the facia back on and you are on your way.
You need to remove the liner on the trunk lid. That will give you access to the license plate lights housing. Remove the sockets by twisting 1/4 turn and replace bulbs. Size for bulbs are 2825
Low beams; If you're sure that the bulbs are both OK, you probably have to replace the turn signal/headlight/dimmer/cruise control switch. I had the same problem on my '96 and replacing the switch solved it. I can't quite remember how that plate light works, but I think it's above the plate in that area across the trunk lid that lights up "PONTIAC" when the lights are on. I had to remove that piece on mine to get the bulbs out. There are about 4 nuts on the inside of the trunk lid that hold the whole thing in. Take it out, replace the bulbs, put it back in place.
Old age and vibration, I'd guess. All of mine were out too. The PONTIAC on the trunk lid wouldn't light up. I replaced the bulbs and now it does. For what it's worth, it's Way Cool when the PONTIAC does light up!
on some cars the tail lights and brake lights are totally different bulbs gain access to the bulbs and have someone push the brakes so that you can determine which bulbs are the brake lights and replace the tail lights
Low beam bulb burnt out? Replace bulb. Bulbs OK? If the dimmer switch is also the turn signal/cruise/headlight on and off switch, you probably have to replace the entire switch.