ECM Power Source Circuit: Description

When the engine switch is turned on (IG), 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 relay (EFI MAIN2) and supplying power to terminal +B and +B2 of the ECM.

If the engine switch is turned off, the ECM holds the EFI relay (EFI MAIN2) ON for a maximum of 2 seconds to allow for the initial setting of the throttle valve.

When the engine switch is turned on (IG), voltage from the ECM's MREL terminal is applied to the EFI relay (EFI MAIN2). This causes the contacts of the EFI relay (EFI MAIN2) to close, which supplies power to terminal +B and +B2 of the ECM.