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 troubleshootingControl module communication bus off
Description
The power steering ecu receives signals from the ecm and the skid control ecu
via the can
communication system.
Hint:
When 2 or more dtcs starting with [u] are output simultaneously, inspect
the connectors and wire
harness of each ecu.
If dtc u0105/41 is output, fi ...
Inspection
Inspect oil pump assembly
Turn the drive gear with 2 screwdrivers and make
sure it rotates smoothly.
Notice:
Be careful not to damage the oil seal lip.
Inspect clearance of oil pump assembly
Push the driven gear to one side of the body. Using
a feeler gauge, measur ...
Disposal
Hint:
When scrapping a vehicle equipped with srs or disposing of
the front seat side airbag, be sure to deploy the airbag first in
accordance with the procedure described below. If any
abnormality occurs with the airbag deployment, contact the
service dept. Of toyota motor sales, u.S.A., Inc.
...