ECU Power Source Circuit: Description
When the ignition switch is turned on (IG), voltage from the ECM's MREL terminal is applied to the EFI relay. This causes the contacts of the EFI relay to close, which supplies power to terminal +B of the TCM.
When the ignition switch is turned on (IG), voltage from the ECM's MREL terminal is applied to the EFI relay. This causes the contacts of the EFI relay to close, which supplies power to terminal +B of the TCM.