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 troubleshootingEcu malfunction
Description
Inspection procedure
If the power steering ecu detects these dtcs, it will shut off the motor
relay circuit (built into the power
steering ecu) and stop power assist. However, power assist continues if dtc
c1533 is output.
Reconfirm dtc
Check for dtc.
Ok:
dtc i ...
Installation
Install generator assembly
Confirm that the wire harness of the crankshaft
position sensor is secured to the wire harness
clamp bracket through the back of the rib of the
timing chain cover.
Install the generator with the 2 bolts.
Torque: 21 n*m (215 kgf*cm, 16 ft.*Lb ...
Front 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 ...