Immobilizer system
The vehicle's keys have built-in transponder chips that prevent the hybrid system from starting if a key has not been previously registered in the vehicle's on-board computer.
Never leave the keys inside the vehicle when you leave the vehicle.
This system is designed to help prevent vehicle theft but does not guarantee absolute security against all vehicle thefts.
The indicator light flashes after the power switch has been turned off to indicate that the system is operating.
The indicator light stops flashing after the power switch has been turned to ACCESSORY or ON mode to indicate that the system has been canceled.

■ System maintenance The vehicle has a maintenance-free type immobilizer system.
■ Conditions that may cause the system to malfunction
Alarm
The alarm
The alarm uses light and sound to give an alert when an intrusion is detected.
The alarm is triggered in the following situations when the alarm is set:
Setting the alarm system
Close the doors and hood, and lock all the doors. The system will be set automatically after 30 seconds.
The indicator light changes from being on to flashing when the system is set.

Deactivating or stopping the alarm
Do one of the following to deactivate or stop the alarms:
(The alarm will be deactivated or stopped after a few seconds.)
■ System maintenance The vehicle has a maintenance-free type alarm system.
■ Items to check before locking the vehicle To prevent unexpected triggering of the alarm and vehicle theft, make sure of the following:
■ Triggering of the alarm The alarm may be triggered in the following situations: (Stopping the alarm deactivates the alarm system.)


■ Alarm-operated door lock In the following cases, depending on the situation, the door may automatically lock to prevent improper entry into the vehicle:
NOTICE
■ To ensure the system operates correctly Do not modify or remove the system. If modified or removed, the proper operation of the system cannot be guaranteed.
Hybrid system precautionsLexus RX (RX 350L, RX450h) 2016-2026 Repair Manual > Smart Access System With Push-button Start (for Start Function): Lost Communication with ECM / PCM (U0100,U0140,U0142,U0155,U1117)
DESCRIPTION These DTCs are stored when there is a CAN communication malfunction between the certification ECU (smart key ECU assembly), ECM, main body ECU (multiplex network body ECU) or combination meter assembly, and data from the option connector (bus buffer ECU) cannot be received. DTC No. ...
Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual > Intuitive Parking Assist System (w/ Intelligent Clearance Sonar System): Control Module Communication Bus "A" Off (U0073,U0155)
DESCRIPTION These DTCs are stored when the clearance warning ECU assembly cannot receive and recognize several signals via the CAN communication line. DTC No. Detection Item DTC Detection Condition Trouble Area U0073 Control Module Communication Bus "A" Off Control module communicat ...