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 troubleshootingTerminals of ecu (2005/11-2006/01)
Check air conditioning amplifier
Measure the voltage and resistance of the
connectors.
Hint:
Check from the rear of the connector while it is
connected to the air conditioning amplifier.
using an oscilloscope, check waveform 1.
Can communication signal
Hint:
...
Unmatched encryption code
Description
This dtc is output when a key with an incomplete key code is inserted into
the ignition key cylinder.
Inspection procedure
Reregister key
Clear the dtc (see page ei-18).
Reregister the key code with the transponder key ecu
(see page ei-5)
Check that the engine ...
Replacement
Replace timing chain cover oil seal
Using a screwdriver and hammer, tap out the oil
seal.
Place the oil seal retainer on wooden blocks.
Apply multi-purpose grease to the lip of a new oil
seal.
Notice:
Keep the lip free of foreign objects.
Using sst and a hammer, tap in a ...