ECM Power Source Circuit [10/2017 - 12/2021]: Description

When the ignition switch is turned to ON, the battery voltage is applied to IGSW of the ECM. The output signal from the MREL terminal of the ECM causes a current to flow to the coil, closing the contacts of the EFI-MAIN NO. 1 relay and supplying power to either terminal +B or +B2 of the ECM.