Auto Shut Down (ASD) Relay

PURPOSE
Relay supplies battery voltage to fuel injectors and ignition coil when energized by Powertrain Control Module (PCM).

OPERATION
The Powertrain Control Module (PCM) energizes ASD relay by supplying relay ground, when ignition switch is in START or RUN position and PCM is receiving a reference signal from distributor.

When the ground is applied, the relay is energized, and voltage is allowed to flow to fuel injectors and ignition coil.

When PCM does not receive reference signal from ignition system, (indicating engine is not running), then the PCM interrupts relay ground circuit and no voltage is supplied to fuel injectors and ignition coil.

The PCM controls fuel pump relay and Auto Shutdown (ASD) relay simultaneously, through same ground circuit.

CIRCUIT OPERATION
The Automatic Shut Down (ASD) relay is located on the front of the right toe box. Power for the coil side of the ASD relay is supplied on circuit A21. This circuit is HOT when the ignition switch is in the START or RUN position.

Ground for the coil side of the relay is controlled by the Powertrain Control Module (PCM) on circuit K51. This circuit connects to cavity 51 of the PCM.

Power for the contact side of the relay is supplied on circuit A14. This circuit is HOT at all times and protected by a fusible link located near the auxiliary jumper post on the left toe box.

When the relay is energized, the contacts in the relay CLOSE connecting circuits A14 and A142. The A142 circuit supplies power to the fuel injectors, heated oxygen sensors, ignition coils, generator, and a ASD relay energized signal to the PCM.