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 troubleshootingRear speed sensor (for 4wd)
Components
Removal
Hint:
Use the same procedures for the lh side and rh 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 termin ...
Disassembly
Remove generator pulley with clutch
Remove the cap from the pulley.
Using a screwdriver, puncture the center of the
cap and pry it off.
Notice:
Do not reuse the cap.
Install sst to the pulley and vise as shown in the
illustration.
Sst 09820-63020
Mount sst (a) i ...
Registration
Hint:
The key has 2 codes: the key code (immobiliser code) and
the wireless code (recognition code). Both of these codes
need to be registered. For wireless code registration
procedures, refer to the following procedures (see page dl-
46). For key code registration procedures, refer to the
pro ...