Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: System Description

SYSTEM DESCRIPTION

IMMOBILISER SYSTEM DESCRIPTION

(a) The immobiliser system determines whether or not to enable starting of the SFI system based on a comparison of the key ID code and the code registered to the vehicle. The immobiliser system compares the ID code registered to the certification ECU (smart key ECU assembly) with the key-embedded transponder chip ID code. If the ID codes do not match, the immobiliser system activates and the SFI system cannot be started. The certification ECU (smart key ECU assembly) manages communication with the SFI system, ID code box (immobiliser code ECU) and steering lock ECU (steering lock actuator or upper bracket assembly). When the ID codes of the transponder chip and certification ECU (smart key ECU assembly) match, the certification ECU (smart key ECU assembly) authorizes the starting of the SFI system.

SYSTEM FUNCTION

(a) Push-button start function

(1) When the driver (or an occupant) gets in the vehicle and depresses the brake pedal while carrying the electrical key transmitter sub-assembly, the certification ECU (smart key ECU assembly) generates a request signal and sends it to the indoor electrical key antenna. When the request signal is received, the indoor electrical key antenna sends another request signal in order to detect whether the electrical key transmitter sub-assembly is in the cabin. When the electrical key transmitter sub-assembly receives this request signal, it sends back an ID code which includes a response code. The ID code sent from the electrical key transmitter sub-assembly is sent to the certification ECU (smart key ECU assembly) via the door control receiver. When the ID code is received, the certification ECU (smart key ECU assembly) analyzes the code.

If the certification result is normal, the smart warning light is displayed on the multi-information display. When the smart warning light is displayed, and the driver presses the engine switch, the certification ECU (smart key ECU assembly) recognizes the engine start signal, turns the ACC relay on and turns the IG relay on, in that order, after 0.025 seconds. At this time, the certification ECU (smart key ECU assembly) confirms that the power source mode has changed and supplies power to the steering lock actuator. Then the steering lock ECU (steering lock actuator or upper bracket assembly) confirms that the certification ECU (smart key ECU assembly) is the proper ECU and operates the steering lock actuator motor until the steering lock is unlocked. After the steering lock is unlocked, the steering lock ECU (steering lock actuator or upper bracket assembly) sends an unlock completion signal to the certification ECU (smart key ECU assembly). When this signal is received, the ID code box (immobiliser code ECU) sends an immobiliser unset command signal to the SFI system after confirming that the certification ECU (smart key ECU assembly) is the proper ECU. Then the certification ECU (smart key ECU assembly) sends a security indicator light off signal to the security indicator light (radio receiver assembly).