ECM Power Source Circuit [11/2017 - ]: Description

When the engine switch is turned on (IG), the battery voltage is applied to the IGSW terminal of the ECM.

The output signal from the MREL terminal of the ECM causes a current to flow to the coil of the semiconductor power integration ECU (EFI-MAIN relay), closing the contacts and supplying power to terminals +B and +B2 of the ECM.