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 the shift lever cannot
be shifted from p
If the shift lever cannot be shifted with your foot on the brake
pedal, there may be a problem with the shift lock system (a system
to prevent accidental operation of the shift lever). Have the
vehicle inspected by your toyota dealer immediately.
The following steps may be used as an emergency ...
Brake switch "A" / "B" correlation
Description
The stop light switch is a duplex system that transmits two signals: stp and
st1-. These two signals are
used by the ecm to monitor whether or not the brake system is working properly.
If the signals, which
indicate the brake pedal is being depressed and released, are detected ...
Pressure sensor circuit
Description
This dtc is output when the refrigerant pressure is either extremely low
(0.19 Mpa [2.0 Kgf/cm2, 28 psi]
or less) or extremely high (3.14 Mpa [32.0 Kgf/cm2, 455 psi] or more). The air
conditioning pressure
sensor, which is installed on the pipe of the high pressure side, detec ...