Why don't your brake lights come on anymore but your turning signals that use the same bulb still function on your 99 Pontiac Sunfire?

It may be as simple as checking the fuse for the brake lights. Also, check the engine compartment fuse block. Your owner's manual has the specs you need. If the brake and turn signal lights use the same bulb, it has a duel element. One element probably blew before the other. Just replace the bulb. Currently having the same problem with my 98. Yes, the lights are dual element but the brake/turn action share the same element, the park light has it's own element. The answer to this problem I found is located closer to the top of the page titled "Why would the third brake light work but the regular ones don't work on a Pontiac Sunfire. I stumble across this today and it seems to be working,