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 troubleshootingRemoval
Disconnect cable from negative battery
terminal
Caution:
Wait at least 90 seconds after disconnecting the
cable from the negative (-) battery terminal to
prevent airbag and seat belt pretensioner activation.
Remove accelerator pedal rod
Disconnect the accelerator pedal position ...
Automatic transaxle unit
Components
...
Check mode procedure
Description
Check mode has a higher sensitivity to malfunctions
and can detect malfunctions that normal mode
cannot detect. Check mode can also detect all the
malfunctions that normal mode can detect. In check
mode, dtcs are detected with 1 trip detection logic.
Check mode pro ...