Hi, there are 3 things that can cause the light to stay on.
One is the parking brake switch, which may have shorted internally or to chassis ground. The switch is above the parking brake pedal. If the connector is still on the switch remove it. If the light goes out, replace the switch.
The second is the fluid level in the master cylinder reservoir. Check fluid level. If good, check the sensor by taking the cable off. If that puts the light out, replace the sensor.
The third is the pressure differential warning switch. The switch turns on when there is a brake failure. You would probably know if this happened. If not, check all wheels for brake fluid leaks. If you have a leak and need help with repair procedures, please get back to me. If you have completed repairs, please read the procedures below from autozone.com to reset the warning switch.
Please let me know if you have any questions and thanks for using FixYa.
A pressure differential warning valve is incorporated in the hydraulic system. The signal from this valve consists of a warning light on the dashboard activated by a differential pressure switch located below the master cylinder. The signal indicates a hydraulic pressure differential between the front and rear brakes of 80-150 psi, and should warn the driver that a hydraulic failure has occurred.
After repairing and bleeding any part of the hydraulic system the warning light may remain on due to the pressure differential valve remaining in the off-center position. To centralize the valve a pressure difference must be created in the opposite branch of the hydraulic system that was repaired or bled last.
Front wheel balancing of cars equipped with disc brakes may also cause a pressure differential in the front branch of the system.
VALVE CENTERING PROCEDURE
- Turn the ignition to either the ACC or ON position.
- Check the fluid level in the master cylinder reservoirs. Fill to within 1 / 4 in. (6mm) of the top if necessary.
- Depress the brake pedal firmly. The valve will centralize itself causing the brake warning light to go out.
- Turn the ignition off.
- Prior to driving the vehicle, check the operation of the brakes and obtain a firm pedal.