I had problems with a brake light constantly burning out. I finally re-grounded the tail light assembly and have not had a problem since. So perhaps the answer to your question is "you have a bad ground". Try it, it is an easy fix.
Day time running lights?
Your Pontiac has a problem in the electronic block, which is controlling the turn signals, the tail and brake lights and etc. It shouldn't be a big deal.
If all of the dashboard lights do not work at the same time on a Pontiac Montana, check the instrument panel relay. The relay is located on the firewall in the engine compartment.
The switch is located on top of the steering column.
Yes, there is a fuse for the interior lights on a 2000 Pontiac Montana. The fuse box is located to the far right of the dash on the passenger side. Open the passenger door to access it.
my turn signals do not work in my 1992 Pontiac Firebird
If you want to turn off the running lights off try to engage the emergency brakes. I have a 2000 Montana and that works.
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.
check the overhead switch make sure its on if not that you have a blown fuse
there is a fuse in the fuse box specifically for automatically turning on lights. I know this because I have my fuse removed. I don't want my lights on all the time.
the control panel on the rear lights goes bad. you can get a new panel on carstuff.com for cheap
Check the bulbs they are double filamented with the smaller for stop and turn signals