ABS Main Relay: Description and Operation

The system relay is used for the operation of the Anti lock Brakes system (ABS) system. Power for the relay is supplied on the B57 circuit from cavity 57 of the Controller Anti Lock Brake (CAB).

Ground for the relay is on the Z1 circuit. This ground is spliced in with the pump motor, and terminates at the right frame rail.

When the system is operating normally, power for the contact side of the relay is supplied from the CAB on the B57 circuit. It passes through the relay to the Z1 ground and terminates at the right frame rail. If a problem is detected in the system, the contact side of the relay switches from the Z1 to the A20 circuit. This causes the ABS warning lamp in the instrument cluster to illuminate.