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 troubleshooting4Wd control ecu communication stop mode
Description
Hint:
For vehicle with 4wd only.
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 ...
When closing the back door
Lower the back door using the
back door handle.
Vehicles without a power back
door
Make sure to push the back door
down from the outside to close it.
Vehicles with a power back
door
The back door closing assist will
activate, and the back door will
fully close automatically.
...
Brake pedal
Components
Removal
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 instrument panel sub-assembly
Remov ...