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 troubleshootingThermostat
Components
Removal
Remove no. 1 Engine under cover
Drain engine coolant (see page co-6)
Remove radiator support opening cover
Disconnect no. 2 Radiator hose
Remove water inlet
Remove the 2 nuts and disconnect the water inlet
from the cylinder block.
Remove thermostat
...
Terminals of ecu
Check tire pressure warning ecu
Disconnect the e56 ecu connector.
Measure the voltage and resistance of the wire
harness side connector.
If the result is not as specified, there may be a
malfunction on the wire harness side.
Reconnect the e56 ecu connector.
Measure the ...
Wireless remote control
The keys are equipped with the
following wireless remote control:
Vehicles without smart key
system
Locks all the doors
Sounds the alarm
Unlocks all the doors
Opens the side windows*
*: This setting must be customized
at your Toyota dealer.
Vehicles with smart key system
Locks all the do ...