Braking Sensor/Switch: Description and Operation

DESCRIPTION
The ABS uses an ABS pedal sensor switch which monitors brake pedal travel and sends this information to the ABS control module through the wire harness. The ABS pedal sensor switch adjustment is critical to pedal feel during ABS cycling. The ABS pedal sensor switch is located in the power brake booster and can be serviced separately.

OPERATION
Anti-lock brake pedal sensor switch operation is as follows:
^ The ABS pedal sensor switch is normally closed. When brake pedal travel exceeds the ABS pedal sensor switch setting during an ABS stop, the ABS control module senses that the ABS pedal sensor switch is open and grounds the pump motor relay coil. This energizes the relay and turns the pump motor on.
^ When the pump motor is running, the brake master cylinder is filled with high-pressure brake fluid and the brake pedal will be pushed up until the ABS pedal sensor switch closes.
^ When the ABS pedal sensor switch closes, the pump motor is turned off and the brake pedal will drop some with each ABS control cycle until the ABS pedal sensor switch opens again and the pump motor is turned on again. This minimizes pedal feedback during ABS cycling.