Hello, it is most likely the turn signal switch or the brake light switch. But first check and make sure there are no blown fuses. Open the trunk and locate the sequencer box. There are 3 wires that feed the brake lights. All should be hot when brakes are applied. Check for juice on the solid green wire, the orange with green strip wire, and the green with orange or red stripe. you can use a test light or volt meter. If the solid green wire is the only one with juice then the turn signal switch is bad. If none of them have juice then check the brake light switch under the dash.
Both wires on that should be hot when the brakes are applied. if none of them have juice then check the 15 amp circuit breaker way up under the dash. usually in the area above the fuse box and headlight switch. It should have full voltage on both sides.
If the turn signal switch is the problem be aware there is a problem with new ones melting due to bad connections at the rivet.
You can search previous threads to see what I'm talking about. As long as your original switch is not melted under the turn signal cam then you most likely can fix it with a new turn signal cam. I recommend tightening up the rivets on the new cam because they have the same problem as the new turn signal switch. Cam is about 75.00 cheaper.