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 troubleshootingMaintenance requirements
To ensure safe and economical driving, day-to-day care and regular
maintenance are essential. It is the owner’s responsibility to
perform regular checks. Toyota recommends the following maintenance:
General maintenance
General maintenance should be performed on a daily basis. This can
be done ...
Head restraints
Head restraints are provided for all seats.
Front seats
Up
Pull the head restraints up.
Down
Push the head restraint down while
pressing the lock release button.
Rear seats
Up
Pull the head restraints up.
Down
Push the head restraint down while
pressing the lock rel ...
Occupant classification ecu
Components
On-vehicle inspection
Inspect occupant classification ecu
(vehicle not involved in collision)
Perform a diagnostic system check (see page rs-
236).
Inspect occupant classification ecu
(vehicle involved in collision)
Perform a diagnostic system check (see p ...