ABS Main Relay: Description and Operation

Control Relay:

The control relay has two purposes. When energized, the relay provides power to the solenoid valves for ABS operation. However, the solenoid valves do not use this power unless the ABS computer completes the circuit to ground. When the solenoid is not energized, it provides a ground path for the antilock warning lamp circuit. Thus, the antilock warning lamp will light when the solenoid relay loses either power or ground. And when energized, the relay provides power to the brake fluid return pump. This action results in the transfer of brake fluid from the accumulator chambers to the master cylinder reservoir. When the pump motor circuit is energized, a PUMP ON reference voltage is sent to the ABS computer.