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 troubleshootingFront lower ball joint
Components
Removal
Hint:
Use the same procedures for the rh side and lh side.
The procedures listed below are for the lh side.
Remove front wheel
Remove front speed sensor lh (for 2wd) (see
page bc-191)
Remove front brake cylinder assembly lh
(see page br-40)
Remove front ...
Push switch / key unlock warning switch malfunction
Description
This dtc is output if the transponder key ecu does not detect that the unlock
warning switch is on even
when the ignition switch is on. Under normal conditions, the unlock warning
switch is on when the
ignition switch is on.
Wiring diagram
Inspection procedure
Re ...
If a warning light turns
on or a warning buzzer
sounds
Calmly perform the following actions if any of the warning lights
comes on or flashes. If a light comes on or flashes, but then
goes off, this does not necessarily indicate a malfunction in the
system. However, if this continues to occur, have the vehicle
inspected by your toyota dealer.
Stop t ...