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 troubleshootingPressure control solenoid "b" electrical (shift solenoid valve sl2)
Description
Shifting from 1st to o/d is performed in combination with the on and off
operation of the shift solenoid
valves sl1 and sl2, which are controlled by the ecm. If an open or short circuit
occurs in any of the shift
solenoid valves, the ecm controls the remaining normal shift sol ...
Glossary of sae and toyota terms
This glossary lists all sae-j1930 terms and abbreviations
used in this manual in compliance with sae
recommendations, as well as their toyota equivalents.
...
Engine (ignition) switch
(vehicles with a
smart key system)
Performing the following operations when carrying the electronic
key on your person starts the engine or changes engine
switch modes.
Starting the engine
Check that the parking brake is set.
Check that the shift lever is set in p.
Firmly depress the brake pedal.
The smart key system in ...