Grand Marquis V8-281 4.6L SOHC (1992)
Pedal Travel Switch: Description and Operation
This system uses a pedal travel switch which monitors brake pedal travel and sends information to electronic control unit (ECU) through the wiring
harness. Switch adjustment is critical to pedal feel during ABS cycling. The switch is mounted on the right side of brake pedal support near the dump
valve adapter bracket.
The switch is normally closed. When brake pedal travel exceeds the switch setting during an anti-lock stop, the electronic controller senses the 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 master
cylinder is filled with high pressure brake fluid and the brake pedal will be pushed up until the switch closes. When the switch closes, the pump is turned
off and pedal will drop with each ABS control cycle until travel switch opens again and pump is turned on again. This minimizes pedal feedback during
ABS cycling.
If pedal travel switch is not adjusted properly or is not electrically connected, it will result in an incorrect pedal feel during ABS stops. Some problems
with the switch or its installation will result in the pump running during entire ABS stop. The pedal will become very firm, pushing the driver's foot up to
an very high position.
