Operation CHARM: Car repair manuals for everyone.

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

Description
When the ignition switch is turned on, battery voltage is applied from the ignition switch to the engine control module. This turns ON the ignition power transistor and energizes the MFI control relay coil. This turns ON the MFI control relay switch and power is supplied from the battery to the engine control module through the MFI control relay switch.