Automatic Shutdown Relay

The Automatic Shutdown (ASD) relay is located in power distribution center near the battery or next to radiator coolant recovery bottle.

The ASD relay is used by the engine controller to supply voltage to fuel pump, fuel injectors and ignition coil. The relay contacts are normally open.

Power is supplied to relay coil when the ignition switch is turned on. The engine controller controls the ground circuit, which energizes the coil and closes the relay contacts.

The engine controller will only ground the relay when ignition switch is in the RUN or START positions and some activity is sensed through the crankshaft position sensor and the synchronization signal in the distributor. If the engine controller senses the RPM signal has stopped, it will remove the ground from relay coil, which will cause the contacts to open and remove power from the circuit.