IS 250 RWD V6-2.5L (4GR-FSE) (2007)
Engine Control Module: Component Tests and General Diagnostics
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 MAIN relay and supplying power to terminal +B of the ECM.
If the engine switch is turned off, the ECM holds the EFI MAIN relay 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 applies to the integration relay (EFI MAIN relay). This causes the
contacts of the integration relay (EFI MAIN relay) to close, which supplies power to terminal +B or +B1 of the ECM.
Wiring Diagram (Part 1)