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

AUTO SHUTDOWN (ASD) RELAY
As one of its functions, the 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.

Power Distribution Center (PDC):

AUTOMATIC SHUTDOWN (ASD) RELAY SENSE-PCM INPUT
A 12 volt signal at this input indicates to the PCM that the ASD has been activated. The ASD relay is located in the Power Distribution Center (PDC). The PDC is located in the engine compartment. Refer to label on PDC cover for relay location. The relay is used to connect the oxygen sensor heater element(s), ignition coil(s) and fuel injectors to 12 volt + power supply.

This input is used to sense that the ASD relay is energized. If the powertrain control module (PCM) does not see 12 volts at this input when the ASD should be activated, it will set a Diagnostic Trouble Code (DTC).

Power Distribution Center (PDC):

AUTO SHUTDOWN (ASD) RELAY-PCM OUTPUT
The ASD relay is located in the Power Distribution Center (PDC).

The ASD supplies battery voltage to the fuel injectors, ignition coil and oxygen (O2S) sensor heating elements. The ground circuit for the coil in the ASD relay is controlled by the powertrain control module (PCM). The PCM operates the relay by switching the ground circuit on and off.