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

PURPOSE
The Power Relay provides Vehicle Power (VPWR) to the Powertrain Control Module (PCM) which then becomes VPWR to the Electronic Engine Control (EEC) system and components that require VPWR to function.

OPERATION
When the ignition switch is turned to the Start or Run position, battery positive (B+) voltage power is applied to the coil of the EEC power relay.

Since the other end of the coil is wired to ground, this energizes the coil and closes the contacts of the EEC power relay. VPWR is now sent to the PCM and the EEC system as VPWR.