It could be brake fluid, badly adjusted emergency brake sensor, some other problem with the brakes... a dealership code scanner can tell you what's wrong.
Bad brake light switch
you need to replace the brake light button under the brakes inside the car
at the top behind brake pedal, don't remove the lower switch it for the cruise control
Check to make sure you have power at the brake light switch, if you have power at the switch, depress the brake pedal, and check for power out of the switch, if no power out with the brake pedal depressed, you need a new brake pedal switch.
If your attempting to install a DVD player (in dash) in your car and need to bypass the brake light wire in order to be able to play it while driving its not too difficult. the brake light wire goes hot when the brake is applyied (to power the brake light itself) the DVD player uses this wire to know when the brake light is on or off based on if the wire is "hot" or not. simply splice the wire into a constant power source like the main power wire to your in dash unit.
1985
If the steering also feels stiff it is probably the electronic brake traction control module. If it pulls to one side while braking it is probably a sticking anti lock brake module.
u need brake fluid or ur braking brake down release it
You have a problem with the brake system. Once you repair the problem the light will reset itself.
the turn signal switch is probably bad
It's the brake pad wear indicator. It indicates worn brake pads that require service. (Source: '97 Catera manual)
there is a fusebox in the trunk (on lefthand wall).