ECM Power Source Circuit: Description

When the ignition switch is turned ON, the battery voltage is applied to terminal IGSW of the ECM. The ECM MREL output signal causes a current to flow to the coil, closing the contacts of the EFI (Marking: EFI MAIN) relay and supplying power to terminal +B of the ECM.

If the ignition switch is turned OFF, the ECM holds the EFI relay ON for a maximum of 2 seconds to allow for the initial setting of the throttle valve.

When the ignition switch is turned ON, voltage from the ECM's MREL terminal flows to the EFI relay. This causes the contacts of the EFI relay to close, which supplies power to terminal +B or +B1 of the ECM.