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

Sent by the fuel injection ECU:

PURPOSE
The system relay (located in center console behind the ash-tray) provides current to the fuel pumps, idle air valve, mass air flow sensor, suppressor relay, oxygen sensor pre-heating resistor and to other ECU controlled functions or components.

OPERATION
The fuel injection ECU controls the relay ground connection. When ground is supplied, the system relay is activated and current can flow to all the related components. If the ground connection is interrupted, no current can reach the components.