The fuse for BOTH brake lights is the same. If one light operates and the other one doesn't it is probably not the fuse.
Check the bulb for need of replacement or perhaps the wire leading to the socket (or the socket itself) is bad.
Check your brake (stop) light fuse
a. is the power on? b. have you put your foot on the brake ? c. has the bulb/fuse gone?
Remove the glove compartment cover and there is a fuse box located behind there
check brake light fuse and brake light switch on pedal
The 1997 Pontiac brake light fuse is located in the fuse box. The brake light fuse will be labeled as the tail light fuse.
On fuse panel under dash to left of steering column.
check the brake light fuse in the dash by your left knee, if it blows, cant shift park
Chjeck the brake light switch located somewhere on the brake pedal lever.
the third brake light is direct from brake light switch no fuse
Should be common to the brake light circuit
Fuse or brake light switch are most likely.
There is no diagram in your owners manual.