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 troubleshootingEngine control system malfunction
Description
If a malfunction in the engine control system is detected, the operations of
vsc and trc are prohibited
by the fail-safe function. When the signals from the engine are input normally,
the fail-safe is canceled and
the dtc is not stored.
Inspection procedure
Check harn ...
Precaution
Caution:
The vehicle is equipped with a supplemental restraint
system (srs), which consists of a steering pad, front
passenger airbag, curtain shield airbag, front seat side
airbag, seat belt pretensioner, center airbag sensor,
front airbag sensor, side airbag sensor, rear airbag
senso ...
Removal
Hint:
Use the same procedures for the rh side and lh side.
The procedures listed below are for the lh side.
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 ...