Main Relay (Computer/Fuel System): Description and Operation

AUTOMATIC SHUTDOWN (ASD) RELAY

As one of its functions, the Automatic Shutdown (ASD) relay will supply battery voltage to the ignition coil. The ground circuit for the ASD relay is controlled by the Powertrain Control Module (PCM). The PCM regulates ASD relay operation by switching the ground circuit on-and-off.

CIRCUIT OPERATION
When the ignition switch is in either the START or RUN position, it connects circuit A1 from fuse 8 in the Power Distribution Center (PDC) to circuit A21. Circuit A21 powers circuit F99 through PDC fuse 18. Circuit F99 feeds the coil side of the Automatic Shut Down (ASD) relay. The Powertrain Control Module (PCM) provides ground for the relay on circuit K900. Circuit K900 connects to cavity C3 of the PCM.

When the PCM grounds the ASD relay, contacts inside the relay close and connect circuit F5 from fuse 20 in the PDC to circuit A142. Circuit A142 splices to, fuel injectors, ignition coil and the upstream and downstream heated oxygen sensors. Circuit A142 also connects to cavity C12 of the PCM.