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 troubleshootingInput speed sensor circuit no signal
Description
This sensor detects the rotation speed of the turbine, which shows the input
revolution of the transaxle. By
comparing the input speed signal (nt) with the counter gear speed sensor signal
(nc), the ecm detects
the shift timing of the gears and controls the engine torque and ...
Fuel pump control circuit
Description
When the engine is cranked, the starter relay drive signal output from the
star terminal of the ecm is
input into the sta terminal of the ecm, and ne signal generated by the
crankshaft position sensor is also
input into the ne+ terminal. Thus, the ecm interprets that the engine is ...
Circuit opening relay
On-vehicle inspection
Disconnect cable from negative battery
terminal
Caution:
Wait at least 90 seconds after disconnecting the
cable from the negative (-) battery terminal to
prevent airbag and seat belt pretensioner activation.
Inspect instrument panel junction block
Notice:
Th ...