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Home >> Lexus >> 2012 >> HS 250h >> Repair and Diagnosis >> Electrical >> Starter >> Smart Access System (For Start Function) (Diagnostics - Introduction) >> SMART ACCESS SYSTEM WITH PUSH-BUTTON START (For Start Function) >> System Description >> System Description
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System Description

  1. PUSH-BUTTON START DESCRIPTION 
    1. The push-button start uses a push-type power switch, which the driver can operate by merely carrying the electrical key. This system consists primarily of the power management control ECU, power switch, transmission control ECU assembly, electrical key, ACC relay, P/POINT relay, IG1 NO. 1 relay, IG1 NO. 2 relay, IG1 NO. 3 relay, IG2 relay, ID code box (immobilizer code ECU) and certification ECU (smart key ECU assembly). The power management control ECU controls the system. This function operates in cooperation with the smart access system with push-button start.

      HINT: 

      In this chapter, the expression "power source" has been used in some locations to allow precise explanations. The power source mode is also expressed using conventional expressions such as "power switch off", "power switch on (ACC)" and "power switch on (IG)".

  2. FUNCTION OF MAIN COMPONENTS 
    Component Function
    Power Switch
    • Transponder Key Amplifier
    • Transmits the power switch signal to the power management control ECU.
    • Informs the driver of the power source mode or system abnormality with the illumination stage of the indicator light.
    • Receives the ID code and transmits it to the certification ECU (smart key ECU assembly) when the key battery is low.
    Electrical Key Receives signals from oscillators and returns its ID code to the entry door control receiver.
    Electrical Key Oscillator
    • Console and Rear Seat
    		 Receives request signals from the certification ECU (smart key ECU assembly) and forms detection areas in the vehicle.
    Power Management Control ECU
    • Changes the power source mode in 4 stages (off, on (ACC), on (IG), on (READY)) in accordance with the shift and stop light switch states.
    • Controls the push-button start function in accordance with signals received from switches and ECUs.
    • The power management control ECU and certification ECU (smart key ECU assembly) permit starting of the hybrid control system after receiving an unlock signal from the transmission control ECU assembly.
    Certification ECU (Smart Key ECU Assembly) Certifies ID the code received from the entry door control receiver and transmits the certification results to the ID code box (immobilizer code ECU) and transmission control ECU assembly.
    Stop Light Switch Outputs the state of the brake pedal to the power management control ECU.
    ID Code Box (Immobilizer Code ECU) Receives gearshift control unlock or engine immobilizer unset signals from the certification ECU (smart key ECU assembly), certifies them, and transmits unset signals to the transmission control ECU assembly and power management control ECU.
    Transmission Control ECU Assembly
    • Locks/unlocks gearshift control based on lock/unlock request signals from certification ECU (smart key ECU assembly).
    • Detects gearshift control lock/unlock status and transmits it to other ECUs.
    • Activates the shift control actuator based on signals from the hybrid vehicle control ECU when gearshift control is unlocked.
    • Controls the application timing of current to the parking lock motor based on signals from the rotation angle sensor.
  3. SYSTEM FUNCTION 

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

    Control Outline
    Power switch control When the person carrying the key enters the vehicle and the brake pedal is depressed, the power management control ECU sends the key certification request signal to the certification ECU (smart key ECU assembly).
    On receiving the key certification request signal, the certification ECU (smart key ECU assembly) generates a request signal and sends it to the indoor electrical key oscillator. The indoor electrical key oscillator transmits the request signal in order to detect that the key is in the cabin.
    When the key receives the request signal, it sends back the response code and ID code.
    When the door control receiver assembly receives the signal from the key, it sends the ID code to the certification ECU (smart key ECU assembly). The ID code box verifies check results received from the certification ECU via LIN and sends them to the power management control ECU. Based on these results, the power management control ECU authorizes the operation of the power switch.
    If the ID codes match, the certification ECU (smart key ECU assembly) sends the certification OK signal to the power management control ECU.
    Upon receiving the certification OK signal, the power management control ECU illuminates the power switch indicator light, changes the power source mode and starts the hybrid control system depending on how the power switch is operated.
    Diagnosis When the power management control ECU detects a malfunction, the power management control ECU diagnoses and memorizes information related to the fault.
  4. CONSTRUCTION AND OPERATION 
    Fig 1: Identifying Power Switch Indicator Light
    GTY197306Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Power Switch

      The power 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 hybrid control system can start in accordance with the illumination state of the indicator light.
      • When the power management control ECU detects an abnormality in the push-button start system, it makes the amber indicator light flash. If the hybrid control system stopped in this state, it may not be possible to restart it.
    2. Indicator Light Condition
      POWER SWITCH INDICATOR LIGHT CONDITION

      Power Source Mode/Condition Indicator Light Condition
      Brake Pedal Released Brake Pedal Depressed, Park (P) selected
      off off Turns on (Green)
      on (ACC, IG) Turns on (Amber) Turns on (Green)
      on (READY) off off
      System malfunction Flashes (Amber) for 15 sec. Flashes (Amber) for 15 sec.
    3. Power Management Control ECU

      The power management control ECU consists of the IG1 NO. 1, IG1 NO. 2, IG1 NO. 3, IG2, ACC, P/POINT relay actuation circuits and CPU.

      HINT: 

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

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

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

      • After approximately 1 hour has elapsed with the power switch on (IG) and park (P) selected, the power management control ECU will automatically cut the power supply (the power source mode will change to off).
      • After approximately 20 minutes has elapsed with the power switch on (ACC) and park (P) selected, the power management control ECU will automatically cut the power supply (the power source mode will change to off).
      • The graphic below shows the transition of power source modes.

        Transition of power source modes:

        Fig 2: Identifying Power Source Mode Graph
        GTY393312Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

        HINT: 

        While the vehicle is being driven normally, operation of the power switch is disabled. However, if the hybrid control system must be stopped in an emergency while the vehicle is being driven, pressing the power switch for 3 seconds or more stops the hybrid control system. The power source mode will change from on (READY) 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 power switch with the brake pedal depressed.
      Fig 3: Identifying Amplifier (Power Switch)
      GTY286916Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. The power management control ECU transmits a key verification request signal to the certification ECU (smart key ECU assembly) when it receives the stop light switch signal.
    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 power 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 management control ECU. The buzzer in the combination meter assembly sounds at the same time.
    8. After the buzzer sounds, if the power switch is pressed within 10 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 be performed using the same procedure as for the key (for standard type).

  7. DIAGNOSIS 

    The power management 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 power switch flashes to warn the driver. At the same time, the ECU stores a 5-digit Diagnostic Trouble Code (DTC) in its 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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