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 troubleshootingComponents
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Luggage room light
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 back door center garnish (see page
ed-59)
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Before refueling the vehicle
Close all the doors and windows, and turn the engine switch to the
“lock” position (vehicles without a smart key system) or off (vehicles
with a smart key system).
Confirm the type of fuel.
Fuel types
Unleaded gasoline (octane rating 87 [research octane number 91] or
higher)
Cauti ...