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 troubleshootingIf you think
something is wrong
If you notice any of the following symptoms, your vehicle probably
needs adjustment or repair. Contact your toyota dealer as
soon as possible.
Visible symptoms
Fluid leaks under the vehicle
(water dripping from the air conditioning after use is normal.)
Flat-looking tires or uneven tire w ...
Data list / active test
Read data list
Hint:
Using the intelligent tester's data list allows switch,
sensor, actuator and other item values to be read without
removing any parts. Reading the data list early in
troubleshooting is one way to save time.
Connect the intelligent tester (with can vim) to the
...
Differential case
Components
Disassembly
Remove front differential ring gear
Place the matchmarks on the ring gear and
differential case.
Remove the 14 bolts.
Using a plastic-faced hammer, tap on the ring gear
to remove it from the case.
Remove front differential case ...