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 troubleshootingFront passenger airbag assembly
Components
On-vehicle inspection
Check front passenger airbag assembly (vehicle not involved in
collision and airbag not deployed)
Perform a diagnostic system check (see page rs-
49).
With the front passenger airbag installed on the
vehicle, perform a visual check:
chec ...
Multiplex communication circuit
Description
The air conditioning amplifier communicates data with the ecm and combination
meter through the can
communication system.
Wiring diagram
Inspection procedure
Check dtc
Clear the dtc (see page ac-31).
Read the dtc (see page ac-31).
Result
Go to can c ...
Communication
Description
When a key is inserted into the ignition key cylinder but no communication
occurs between the key and
transponder key ecu, dtc b2796 is output. When a key is inserted into the
ignition key cylinder but a
communication error occurs between the key and transponder key ecu, dtc b ...