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Home >> Lexus >> 2014 >> IS F >> Repair and Diagnosis >> Electrical >> Starter >> Smart Access System (Keyless Start) (Diagnostics - Introduction) >> SMART ACCESS SYSTEM WITH PUSH-BUTTON START (for Start Function) >> System Description [09/2013 - ] >> System Description [09/2013 - ]
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System Description [09/2013 - ]

  1. PUSH-BUTTON START DESCRIPTION 
    1. The push-button start uses a push-type engine switch, which the driver can operate by merely carrying the electrical key. This system consists primarily of the power source control ECU, engine switch, ID code box (immobilizer code ECU), steering lock ECU, electrical key, ACC relay, IG1 relay, IG2 relay and certification ECU (smart key ECU assembly). The power source control ECU controls the system. This function operates in cooperation with the smart access system with push-button start.
  2. FUNCTION OF COMPONENT 
    Component Function
    Engine Switch
    • Transponder Key Amplifier
    • Transmits engine switch signal to power source control ECU.
    • Informs driver of a power source mode or system abnormality with illumination stage of indicator light.
    • Receives ID code and transmits it to certification ECU (smart key ECU assembly) when the key battery is low.
    Electrical Key Receives signals from oscillators and returns ID code to entry door control receiver.
    Electrical Key Oscillator
    • Console and Rear Seat
    		 Receives request signals from certification ECU (smart key ECU assembly) and forms detection area in vehicle interior.
    Entry Door Control Receiver Receives ID code from electrical key and transmits it to the certification ECU (smart key ECU assembly).
    Power Source Control ECU
    • Changes power source mode in 4 stages (off, on (ACC), on (IG), start) in accordance with shift position and state of stop light switch.
    • Controls push-button start function in accordance with signals received from switches and each ECU.
    Certification ECU (smart key ECU assembly) Certifies the ID code received from entry door control receiver and transmits certification results to the ID code box (Immobiliser Code ECU) and steering lock ECU.
    Stop Light Switch Outputs state of brake pedal to power source control ECU.
    ID Code Box (immobilizer code ECU) Receives steering unlock or engine immobilizer unset signals from certification ECU (smart key ECU assembly), certifies them, and transmits each unset signal to steering lock ECU or ECM.
    ECM
    • Receives engine start request signal from power source control ECU, turns ON STARTER relay, and starts engine.
    • Receives signal from ID code box (Immobiliser Code ECU) and performs engine ignition and injection.
  3. SYSTEM FUNCTION 

    The electric controls of the push-button start function are described below:

    Control Outline
    Engine switch control
    • When driver operates engine switch with electrical key in driver's possession, certification ECU (smart key ECU assembly) starts indoor electrical key oscillator, which transmits request signal to electrical key. Upon receiving this signal, the electrical key transmits ID code signal to power source control ECU.
    • ID code box (immobilizer code ECU) verifies check results received from the certification ECU (smart key ECU assembly) via LIN and sends them to power source control ECU. Based on these results, power source control ECU authorizes operation of engine switch.
    Diagnosis When power source control ECU detects malfunction, the power source control ECU diagnoses and memorizes the failed section.
  4. CONSTRUCTION AND OPERATION 
    Fig 1: Indicator Light On Engine Switch
    GTY104304Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Engine Switch

      The engine switch consists of a momentary type switch, 3 color (amber, green, greenish white) LEDs, and a transponder key amplifier.

      • The greenish white LED is for illumination.
      • The amber and green LEDs are for the indicator lights. The driver can check the present power source mode and whether the engine can start in accordance with the illumination state of the indicator light.
      • When the power source control ECU detects an abnormality in the push-button start system, it makes the amber indicator light flash. If the engine stopped in this state, it may not be possible to restart it.
    2. Indicator Light Condition
      ENGINE SWITCH INDICATOR LIGHT CONDITION

      Power Source Mode/Condition Indicator Light Condition
      Brake pedal released Brake pedal depressed, shift lever in P or N
      off OFF Turns ON (Green)
      on (ACC, IG) Turns ON (Amber) Turns ON (Green)
      Engine running OFF OFF
      Steering lock not unlocked Flashes (Green) for 15 sec. Flashes (Green) for 15 sec.
      System malfunction Flashes (Amber) for 15 sec. Flashes (Amber) for 15 sec.
    3. Power Source Control ECU

      The power Source Control ECU consists of the IG1 and IG2 relay actuation circuits and CPU.

      HINT: 

      Before removing the battery, make sure to turn the engine switch off. The power source control ECU constantly stores the present power source mode in its memory. Therefore, if the power source control ECU is interrupted by disconnecting the battery, the power source control ECU restores the power source mode after the battery is reconnected. For this reason, if the battery is disconnected when the engine switch is other than off, the power will be restored to the vehicle at the same time the power is restored to the power source control ECU (by reconnecting the battery).

  5. PUSH-BUTTON START FUNCTION OPERATION 
    1. This system has different power source mode patterns depending on the brake pedal condition and shift lever position.
      Brake Pedal Shift Lever Power Source Mode Pattern
      Depressed P or N When the engine switch is pushed once.
      • off → engine start
      Not depressed P Each time the engine switch is pushed.
      • off → on (ACC) → on (IG) → off
      Except P Each time the engine switch is pushed.
      • off → on (ACC) → on (IG) → on (ACC)
      - P When the engine switch is pushed in the on (IG) condition (engine running).
      • on (IG) → off
      - Except P When the engine switch is pushed in the on (IG) condition (engine running).
      • on (IG) → on (ACC)

      When the battery of the key is low, the push-button start function can be operated by holding the key against the engine switch.

      • After approximately 20 minutes has passed with the engine switch on (ACC) and the shift position in P, the power source control ECU will automatically cut the power supply (the power source mode changes to off).
      • The illustration below shows the transition of power source modes.

        Transition of power source mode:

        Fig 2: Transition Of Power Source Mode Chart
        GTY407878Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

        HINT: 

        While the vehicle is being driven normally, operation of the engine switch is disabled. However, if the engine must be stopped in an emergency while the vehicle is being driven, pressing the engine switch for 3 times quickly or pressing and holding the engine switch for 2 seconds or more stops the engine. Power source mode changes from start to on (ACC).

  6. WHEN KEY BATTERY IS LOW 
    1. To operate the push-button start function when the key battery is low, hold the key close to the engine switch with the brake pedal depressed.
      Fig 3: Operating Push-Button Start Function When Key Battery Is Low
      GTY141007Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. The power source control ECU transmits a key verification request signal from the stop light switch to the certification ECU (smart key ECU assembly).
    3. The certification ECU (smart key ECU assembly) does not receive an ID code response from the entry door control receiver, so it actuates the transponder key amplifier built into the engine switch.
    4. The transponder key amplifier outputs an engine immobilizer radio wave to the key.
    5. The key receives the radio wave, and returns a radio wave response to the transponder key amplifier.
    6. The transponder key amplifier combines the key ID codes with the radio wave response, and transmits it to the certification ECU (smart key ECU assembly).
    7. The certification ECU (smart key ECU assembly) judges and verifies the ID code, and transmits a key verification OK signal to the power source control ECU. The buzzer in the combination meter sounds at the same time.
    8. After the buzzer sounds, if the engine switch is pressed within 5 seconds with the brake pedal not depressed, the power source mode changes to on (ACC) or on (IG), the same as in the normal condition.

      HINT: 

      The key (for card type) operation inspection can performed using the same procedure as for the key (for standard type).

  7. DIAGNOSIS 

    The power source control ECU can detect malfunctions in the push-button start function when the power source mode is on (IG).

    When the ECU detects a malfunction, the amber indicator light of the engine switch flashes to warn the driver. At the same time, the ECU stores a 5-digit DTC (Diagnostic Trouble Code) in the memory.

    • The indicator light warning continues for 15 seconds even after the power source mode is changed to off.
    • The DTC can be read by connecting the Techstream to the DLC3.
    • The push-button start function cannot be operated if a malfunction occurs.
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