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 troubleshootingReassembly (2005/11-2006/01)
Install front drive shaft bearing
Using sst and a press, press in the drive shaft
bearing to the inboard joint rh.
Sst 09527-10011, 09710-04081
Notice:
The bearing should be installed completely.
Using a snap ring expander, install a new drive shaft
hole snap ring.
...
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.
Disconnect cable from positive battery
terminal
Remove battery clamp
...
Data list / active test
Read data list
Hint:
Using the intelligent tester's data list allows switch,
sensor, actuator and other item values to be read without
removing any parts. Reading the data list early in
troubleshooting is one way to save time.
Connect the intelligent tester (with can vim) to the
dlc3 ...