The theory again....
Description and Operation
LOCATION
Relay is mounted in engine compartment, on the left inner fender.
PURPOSE
Relay supplies battery voltage to fuel pump and oxygen sensor heater element when energized by Powertrain Control Module (PCM).
OPERATION
PCM energizes fuel pump relay by supplying relay ground, when ignition switch is in START or RUN position and PCM is receiving a reference signal from distributor.
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 pump, ignition coil, or oxygen sensor heater element.
PCM controls fuel pump relay and Auto Shutdown (ASD) relay simultaneously, through same ground circuit.
