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

PURPOSE
The Multiport Fuel Injection (MFI) relay provides power to the ECM and the fuel pump.

OPERATION
While the ignition switch is ON, battery positive voltage is supplied to the engine control module, injectors, volume air flow sensor, etc. When the ignition switch is turned to the ON position, battery positive voltage is supplied from the ignition switch to the engine control module. When battery positive voltage is supplied to the engine control module, the power transistor is switched ON and current flows to the MFI relay coil. As a result, the MFI relay switch is switched ON, and power is supplied, by way of the MFI relay switch, from the battery to the engine control module.