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 troubleshootingTransmission fluid temperature sensor "A" performance
Description
Refer to dtc p0710 (see page ax-46).
Monitor description
This dtc indicates that there is a problem with output from the atf
temperature sensor and that the
sensor itself is defective. The atf temperature sensor converts the atf
temperature to an electrical
resistance v ...
Terminals of ecu
Check occupant classification ecu
Measure the voltage of the connector.
...
Compressor circuit
Description
When the a/c switch is turned on, the magnetic clutch on signal is sent from
the air conditioning
amplifier. Then the mg clt relay turns on to operate the magnetic clutch.
Wiring diagram
Inspection procedure
Inspection procedure
Perform active test by intelligent tester (a ...