Circuit Description

When the ignition switch is turned ON, battery positive voltage is applied to terminal IGSW of the ECM and the EFI or ECD relay control circuit in the ECM sends a signal to terminal MREL of the ECM switching on the EFI or ECD relay.

This signal causes current to flow to the coil, closing the contacts of the EFI or ECD relay and supplying power to terminal +B of the ECM.