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

PURPOSE/OPERATION
While the ignition switch is ON, battery power supply is supplied to the engine control module, injectors, volume air-flow sensor, etc.
Turning the ignition switch to the ON position causes current to flow from the ignition switch through the multiport fuel injection relay coil to ground. This turns the multiport fuel injection relay switch on and supplies power from the battery to the engine control module via the multiport fuel injection relay switch.