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 troubleshootingVc output circuit
Description
The ecm constantly generates 5 v power from the battery voltages supplied to
the +b (batt) terminal to
operate the microprocessor. The ecm also provides this power to the sensors
through the vc output
circuit.
When the vc circuit is short-circuited, the microprocessor in the ...
Dtc check / clear
Check dtc
Dtcs which are stored in the ecm can be displayed
with the intelligent tester.
The intelligent tester can display pending dtcs and
current dtcs. Some dtcs are not stored unless a
malfunction is detected in consecutive driving
cycles. When a malfunction is detected ...
Inspection
Inspect starter assembly
Notice:
These tests must be performed within 3 to 5 seconds
to avoid burning out the coil.
Perform the pull-in test.
Disconnect the lead wire from terminal c.
Connect the battery to the magnetic switch as
shown in the illustration. Check that the clutch ...