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 troubleshootingCoolant
Replacement
Remove no. 1 Engine under cover
Drain engine coolant
Loosen the radiator drain cock plug.
Hint:
Collect the coolant in a container and dispose of it
according to the regulations in your area.
Remove the radiator reservoir cap.
Caution:
Do not remove the radiator ...
Air-fuel ratio (a/f) and heated oxygen (ho2) sensor
heater monitors (front a/f and rear ho2 sensor type)
Preconditions
The monitor will not run unless:
The mil is off.
Drive pattern
Connect the intelligent tester to the dlc3.
Turn the ignition switch on.
Turn the tester on.
Clear dtcs (if set) (see page es-35).
Start the engine.
Allow the engine to idle for 10 minute ...
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 ...