The engine immobiliser system is designed to prevent the vehicle from being stolen. This system uses a transponder key ecu that stores the key codes of authorized ignition keys. If an attempt is made to start the engine using an unauthorized key, the ecu sends a signal to the ecm to prohibit fuel delivery and ignition, effectively disabling the engine.

The transponder key coil receives this signal, the transponder key amplifier amplifies it, and then the signal is transmitted to the ecu. The ecu matches the key's id code with the vehicle's id code, which was previously registered in the ecu and then communicates the results to the ecm using sfi communication.
Engine immobiliser system
How to proceed with troubleshootingPower supply relay failure
Description
If the power steering ecu detects these dtcs, it shuts off the motor relay
circuit (built into the power
steering ecu) and stops power assist.
Inspection procedure
Reconfirm dtc
Check for dtc.
Ok:
dtc is not output.
Replace power steering ecu ...
Terminals of ecu
Check instrument panel junction block (main body ecu)
Measure the voltage of the connectors.
If the result is not as specified, the junction block
(main body ecu) may have a malfunction. ...
Slip indicator light remains on
Description
The slip indicator blinks during vsc and/or trc operation.
When the system fails, the slip indicator comes on to warn the driver.
For 2wd: with auto lsd switch on, when the hydraulic brake booster is at a high
temperature, the slip
indicator illuminates.
Wiring diagram
In ...