Circuit Description

When the brake pedal is depressed, the contacts on the brake light switch close to illuminate the brake lights. Battery voltage is also applied to terminal 14 of the electronic brake control module (EBCM), which signals the antilock brake system (ABS) controller that the brakes are applied and ABS may be needed. Without this, signals from a wheel speed sensor that may indicate a need for ABS intervention are questionable. When the brake pedal is not depressed, the EBCM terminal 14 is grounded through the brake lights.

This procedure will check whether there is no output or constant output from the brake light switch and will determine the cause as a faulty switch or a problem in the circuitry.