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PUSH-BUTTON START DESCRIPTION

  1. The push-button start uses a push-type engine switch, which the driver can operate by merely carrying the key. This system consists primarily of the main body ECU, engine switch, ID code box, steering lock ECU, key, D-ACC relay, D-IG1 relay, IG2 relay and certification ECU. The main body ECU controls the system. This function operates in cooperation with the entry and start system. The table below shows the transition of the engine switch, which depends on whether the brake pedal is depressed or released.

  2. This system has different power source mode patterns depending on the brake pedal and shift lever conditions.

    Condition
    		Power Source Mode Pattern
    Brake pedal not depressed, shift lever in P
    		Each time engine switch is pushed
    1. off → on (ACC) → on (IG) → off
    Brake pedal not depressed
    		When engine switch is pushed in engine started condition
    1. Engine started → off
    Brake pedal depressed, shift lever in P or N
    		When engine switch is pushed once
    1. off → engine start
    Brake pedal depressed, shift lever in P or N
    		When engine switch is pushed in on (ACC) condition
    1. on (ACC) → engine start
    Brake pedal depressed, shift lever in P or N
    		When engine switch is pushed in on (IG) condition
    1. on (IG) → engine start
    Brake pedal depressed
    		When engine switch is pushed in engine started condition
    1. Engine started → off
    When the battery of the key or card key is low, the push-button start function can be operated by touching the key or card key to the engine switch.


FUNCTION OF COMPONENT

Components
Function
Engine Switch
(Transponder Key Amplifier)
  1. Transmits engine switch signal to main body ECU.
  2. Informs driver of power source mode or system abnormality with indicator light illumination.
  3. Receives ID code and transmits it to certification ECU when key or card key battery is low or affected by wave noise, etc.
Key
  1. Receives signals from oscillators and returns ID code to entry door control receiver.
Indoor Key Oscillator
  1. Receives request signal from certification ECU and forms detection area in vehicle interior.
Door Control Receiver
  1. Receives ID code from key and transmits it to certification ECU.
Main Body ECU
  1. Changes power source mode in 4 stages (off, on (ACC), on (IG), start) in accordance with state of park / neutral position switch.
  2. Controls push-button start function in accordance with signals received from switches and each ECU.
Certification ECU
  1. Certifies ID code received from entry door control receiver and transmits certification results to ID code box and steering lock ECU.
Park / Neutral Position Switch
  1. Outputs state of shift position to main body ECU.
Stop Light Switch
  1. Outputs state of brake pedal to main body ECU.
ID Code Box
  1. Receives steering unlock or engine immobiliser unset signals from certification ECU, certifies them, and transmits each unset signal to steering lock ECU or ECM.
ECM
  1. Receives engine start request signal from power source control ECU, turns ON ST relay, and starts engine.
  2. Receives signal from ID code box and performs engine ignition and fuel injection.

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

Control
Outline
Engine Switch Control
  1. When driver operates engine switch with key in driver's possession, certification ECU starts indoor key oscillator, which transmits request signal to key. Upon receiving this signal, key transmits ID code signal to door control receiver.
  2. ID code box verifies check results received from certification ECU via LIN line and sends them to main body ECU. Based on these results, main body ECU authorizes operation of engine switch.
Diagnosis
  1. When main body ECU detects malfunction, main body ECU diagnoses and memorizes failed section.

CONSTRUCTION AND OPERATION
A109251E02

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

    1. The greenish white LED is for illumination.
    2. 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 or not in accordance with the illumination state of the indicator light.
    3. When the main body ECU detects an abnormality in the entry and start system, it makes the amber indicator light flash. If the engine is stopped in this state, it might 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, key certification passed
    Off
    		OFF
    		Illuminates (green)
    On (ACC, IG)
    		Illuminates (amber)
    		Illuminates (green)
    Engine running
    		OFF
    		OFF
    Steering lock locked
    		Flashes (green) for 30 seconds
    		Flashes (green) for 30 seconds
    System malfunction
    		Flashes (amber) for 15 seconds
    		Flashes (amber) for 15 seconds
    Stop light switch with shift lever in P or N malfunction
    		Flashes (green) for 15 seconds
    		Flashes (green) for 15 seconds

  3. Main body ECU:
    The main body ECU consists of the D-IG1 relay, D-ACC relay and IG2 relay actuation circuits and CPU.


SYSTEM NOT OPERATING NORMALLY (DUE TO KEY BATTERY DEPLETION, ELECTRICAL NOISE, ETC.)
A158346E01

  1. To operate the push-button start function when the key or card key battery is low or affected by wave noise, etc., touch the LEXUS mark of the key or card key to the engine switch while depressing the brake pedal with the shift lever in P or N.

  2. The main body ECU transmits a key verification request signal from the stop light switch to the certification ECU.

  3. The certification ECU does not receive an ID code response from the door control receiver, so it actuates the transponder key amplifier built into the engine switch.

  4. The transponder key amplifier outputs an engine immobiliser 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.

  7. The certification ECU judges and verifies the ID code, and transmits a key verification OK signal to the main body ECU. The buzzer in the combination meter sounds at the same time.

  8. After the buzzer sounds, with the shift lever in P or N, if the engine switch is pressed within 10 seconds with the brake pedal not depressed, the power source mode changes to on (ACC) or on (IG), as in the normal condition.


DIAGNOSIS
The main body 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 the 5-digit DTC (Diagnostic Trouble Code) in the memory.
  1. The indicator light warning continues for 15 seconds even after the power source mode is changed to off.
  2. The DTC can be read by connecting the intelligent tester to the DLC3.
  3. The push-button start function cannot be operated if a malfunction occurs.