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 troubleshootingSteering angle sensor communication stop mode
Description
Wiring diagram
Inspection procedure
Notice:
Turn the ignition switch off before measuring the resistances of the
main wire and the branch
wire.
After the ignition switch is turned off, check that the key reminder
warning system and light
reminder warning system ...
Dtc check / clear
Check dtc
Hint:
When dtc b1650/23 is detected as a result of
troubleshooting for the airbag system, troubleshoot
the occupant classification system.
Use the intelligent tester (with can vim) to read and
clear dtcs, otherwise the dtcs cannot be read and
cleared.
Connect ...
Transmission fluid temperature sensor "A" performance
Description
Refer to dtc p0710 (see page ax-46).
Monitor description
This dtc indicates that there is a problem with output from the atf
temperature sensor and that the
sensor itself is defective. The atf temperature sensor converts the atf
temperature to an electrical
resistance v ...