LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2005 >> LS 430 >> Repair and Diagnosis >> Body & Frame >> Door Locks >> Smart Key System - Diagnostics >> System Description
April 5, 2026: LEMON Manuals is launched! Read the announcement.

System Description

  1. SMART KEY SYSTEM DESCRIPTION 
    1. In addition to conventional mechanical key and wireless door lock remote control functions, the smart system enables door locking/unlocking, steering lock releasing, engine starting and trunk opening without operating the key. The only requirement is that the key be in the driver's possession.
    • This system is controlled by the theft warning ECU. When the theft warning ECU detects the presence of the smart key in one of the detection area, it identifies and checks the ID code, and outputs operation signals to the related ECUs in accordance with their functions.
    • The detection areas are formed by 8 oscillators (4 door oscillators, 2 trunk oscillators, and 2 room oscillators).
    • The smart function is only available for the master key and is not available for the sub-key and flat key.
  2. Function of Main Component 
    Fig 1: Function Of Main Component Description Chart
    G03002884Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  3. System Function 
    1. The smart key system has the following functions:
    Fig 2: Smart Key System Description Chart
    G03002885Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  4. Warning Function 
    1. General

    The smart key system is equipped with a warning function to prevent problems resulting from errors in smart key usage. The smart key system works without any requirements from the driver other than having the key in one's possession. The driver, as a result, may become unaware of the presence or location of the key and make errors (listed below) that could lead to serious problems.

    Examples: 

    1. The driver is unaware that the key has been taken out of the vehicle by a passenger.
    2. The driver exits the vehicle with its engine running.
    3. The driver exits the vehicle with its shift lever in a position other than "P".

    If the above situations occur, the engine may be unable to be started once it has been turned off, the vehicle may be stolen, or other problems may follow. Warning function descriptions for several smart key usage errors are below.

    1. Assumption: While the shift lever is in P and the ignition switch is not turned to LOCK, the driver or a passenger takes the smart key out of the vehicle.

      Possible result without warning: Vehicle theft or inability to restart engine.

      Fig 3: Warning Function - (While Shift Lever Is In P And Ignition Switch Is Not Turned To LOCK)
      G03002886Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Assumption: Doors are locked without turning the ignition switch to LOCK. Possible result without warning: Vehicle theft or inability to restart engine.
      Fig 4: Warning Function - (Doors Are Locked Without Turning Ignition Switch To Lock)
      G03002887Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Assumption: While the shift lever is not in P position and the ignition switch is not turned to LOCK, the driver is about to exit the vehicle.

    Possible result without warning: Vehicle theft or inability to restart engine.

    Fig 5: Warning Function - (While Shift Lever Is Not In P Position And Ignition Switch Is Not Turned To LOCK)
    G03002888Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Assumption: While the shift lever is not in P position, a passenger takes the smart key out of the vehicle.

    Possible result without warning: Inability to restart engine.

    Fig 6: Warning Function - (While Shift Lever Is Not In P Position)
    G03002889Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Assumption*: A passenger takes the smart key out of the vehicle together with luggage.

    HINT:

    This assumption is not default setting.

    Possible result without warning: Inability to restart engine.

    Fig 7: Warning Function - (Passenger Takes Smart Key Out Of Vehicle Together With Luggage)
    G03002890Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Assumption: An attempt is made to lock the doors while the smart key is inside the vehicle. Possible result without warning: Vehicle theft
    Fig 8: Warning Function - (While Smart Key Is Inside Vehicle)
    G03002891Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Assumption: An attempt is made to lock a door that is ajar. Possible result without warning: Vehicle theft or battery depleted
      Fig 9: Warning Function - (Attempt Is Made To Lock A Door That Is Ajar)
      G03002892Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Assumption: The voltage of the smart key has dropped.

      Possible result without warning: Smart control is suddenly disabled.

      DETECTION CONDITION

      Detection Condition When condition given below is met, vehicle interior check is performed and code indicating voltage drop of smart key battery is received, warning is issued.
       
      • When ignition switch has been ON for approximately 20 minutes or more, and then turned OFF.
      Warning (Buzzer - in combination meter) Sounds once upon detection.
      Warning (Multi-information Display) "Low Key Battery" appears for approximately 5 seconds.
      Warning (Wireless Door Lock Buzzer) -
    1. Assumption: The smart key is placed outside the smart key detection area (in the glove box or on the floor mat).

      Possible result without warning: Driver confusion.

      DETECTION CONDITION

      Detection Condition If condition given below is met and vehicle interior check fails, warning is issued.
       
      • Ignition switch is pushed.
      Warning (Buzzer - in combination meter) Sounds once upon detection.
      Warning (Multi-information Display) "Key is not Detected" appears for approximately 5 seconds.
      Warning (Wireless Door Lock Buzzer) -
scientia non olet · About LEMON Manuals