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

Relay Locations:

PURPOSE
Relay supplies battery voltage to the ignition coil and fuel injector(s).

OPERATION
Ignition switch in the START or RUN position, and PCM is receiving reference signals from the distributor pick-up.

The Powertrain Control Module (PCM) activates the relay (by supplying a ground).

If the PCM does not receive a signal from the distributor pick-up, (engine not running), the PCM interrupts the relay ground and no voltage is supplied to the ignition coil, or fuel injector(s).

NOTE: The PCM controls the Auto Shutdown (ASD) and fuel pump relays simultaneously, through the same ground circuit.