Section 416 (Engine Immobilizer System - Diagnosis): Description
WARNING: This page is about a different car, the 2004 Lexus ES 330. However, it is still accessible from the selected car via links, so may be relevant.
The engine immobilizer system has been designed to prevent the vehicle from being stolen. This system uses a transponder key ECU that stores the key code of the authorized ignition key. If an attempt is made to start the engine using a non-authorized key, the transponder key ECU sends a signal to the ECM to prohibit fuel delivery and ignition, effectively disabling the engine.
NOTE:
After replacing the transponder key ECU, the engine will not start if the ignition switch has been repeatedly turned on/off more than 20 times before performing the communication code initialization process.
The engine will start only when the transponder key ECU is replaced with a new one.