STOP AND START SYSTEM Backup Boost Converter Circuit

DESCRIPTION

A backup boost converter is built into the engine stop and start ECU.

The backup boost converter and eco run vehicle converter assembly (external backup boost converter) help maintain the power source voltage when the engine is restarted by stop and start control.

This prevents various functions such as the audio and visual system from malfunctioning if the power source voltage drops due to the battery voltage dropping when the engine is restarted by stop and start control.

If any DTCs are output, troubleshoot the DTCs first.

Tech Tips

A relay function and fuse function are provided in the backup boost converter and eco run vehicle converter assembly (external backup boost converter).

If there is a malfunction in any of the electrical system circuits connected to the backup boost converter and eco run vehicle converter assembly (external backup boost converter), the fuse and relay functions shut off the malfunctioning circuit to protect other circuits (remains shut off until next trip).

When the electrical system circuit is shut off, power to the circuit is cut off, causing any systems connected to the circuit to be disabled.

The fuse function is reset* when the engine switch is turned off. If the malfunction still exists in the electrical system circuit that has been shut off by the relay function, it will be shut off again by the relay and fuse functions the next time the engine switch is turned on (IG).

*: A semiconductor fuse self resets according to electric signal.


    The backup boost converter supplies power to:

  • Navigation system

  • Audio and visual system

  • Air conditioning system

  • Tire pressure warning system

  • Lane departure alert system

  • Auto glare-resistant EC mirror

  • Cruise control system

  • CAN communication system

  • Dynamic radar cruise control system

  • Lighting system

  • Blind spot monitor system

WIRING DIAGRAM

Refer to B22C0 Click here.

CAUTION / NOTICE / HINT

Note


  • Before replacing the engine stop and start ECU, read the number of starter operations and write it into a new engine stop and start ECU Click here.

  • After replacing the engine stop and start ECU or air conditioning amplifier assembly, reset and perform learning of the air conditioning information in the engine stop and start ECU Click here.

  • After replacing the engine stop and start ECU or airbag sensor assembly, clear and calibrate the deceleration sensor zero point in the engine stop and start ECU Click here.

  • Inspect the fuses for circuits related to this system before performing the following inspection procedure.

PROCEDURE


  1. CHECK PROBLEM SYMPTOM


    1. Determine the trouble area by referring to the table below.

      Effect on Vehicle Trouble Area/Cause Fail-safe DTC Output Stop and start cancel indicator light Proceed to Symptom

      When the engine is restarted by stop and start control:

      The following symptoms may occur.


      • Audio and visual system is reset

      • The combination meter assembly fades in and out

      • The steering wheel feels heavy when the engine is restarted*

      *A DTC may be stored in the power steering system

      Backup boost converter internal malfunction


      • Internal power source malfunction

      • Internal power source overvoltage

      • CPU duty malfunction

      • Communication cycle error

      		 Stop and start system control prohibited P323B Blinks A Systems stop operating during engine restart as the backup boost converter output voltage cannot be boosted
      Battery voltage drop

      Systems on the converter output side do not operate

      B41 terminal : All of the following will not operate


      • Air conditioning system

      • Lighting system

      • Tire pressure warning system

      B42 terminal : All of the following will not operate


      • Navigation system

      • Audio and visual system

      B43 terminal : All of the following will not operate


      • Navigation system

      • Lighting system

      • Audio and visual system

      IG41 terminal : All of the following will not operate


      • Air conditioning system

      • Tire pressure warning system

      • Lane departure alert system

      • Auto glare-resistant EC mirror

      • Blind spot monitor system

      • CAN communication system

      • Dynamic radar cruise control system

      		 Overcurrent applied to an output terminal (output terminal relay circuit is shutoff) Stop and start system control is prohibited (Connected ECU or sensors may detect power source malfunction DTCs) B22C0 Blinks A Systems do not operate as power supply from the converter is cut off

      Systems do not operate (Due to converter input side malfunction)

      ACC terminal: All of the following do not operate


      • Navigation system

      • Telematics system

      IG1 terminal: All of the following do not operate


      • Vehicle stability control system

      • Power steering system

      • Air conditioning system

      • Tire pressure warning system

      • Lane departure alert system

      • Auto glare-resistant EC mirror

      • Blind spot monitor system

      • CAN communication system

      • Dynamic radar cruise control system

      IG2 terminal: The meter / gauge system will not function

      ILL terminal: All of the following do not operate


      • Navigation system

      • Air conditioning system

      Converter input circuit malfunction


      • Open or short to GND in IG1 circuit

      • Open or short to GND in IG2 circuit

      • Open or short to GND in ACC circuit

      		 Stop and start control prohibited - Does not blinks (Blinks when communication error DTCs are stored) B Systems do not operate as power supply from the converter is cut off

      Systems on the converter output side do not operate (varies depending on the malfunctioning relay circuit the converter detected)

      B12 terminal: The telematics system will not function

      Malfunction in circuits the converter supplies power to

      (between converter and ECUs or sensors)


      • Open or short in the combination meter assembly circuit

      		 Related systems do not operate as the relay circuit in the converter is turned off - Does not blink (Blinks when communication error DTCs are stored) B Systems do not operate as power supply from the converter is cut off

      All of the following will occur


      • Vehicle stability control system

      • Power steering system

      • Meter / gauge system

      • Navigation system

      • Audio and visual system

      • Telematics system

      • Air conditioning system

      • Lighting system

      • Tire pressure warning system

      • Lane departure alert system

      • Auto glare-resistant EC mirror

      • Blind spot monitor system

      • CAN communication system

      • Dynamic radar cruise control system

      • Open in BBC fuse circuit

      • Short in converter circuit

      • Backup boost converter malfunction

      		 Stop and start control prohibited P0617 Does not blink (Due to disabled meter/gauge system) A All systems that the converter supplies power to do not operate (see circuit diagram)
      P323B
      The audio does not operate (until the engine switch is turned off) Excessive audio volume Data List item "State of External BBC" displays "Overload" while the circuit is protected The relay circuit in the converter is turned off to cut off power supply to the audio and visual system (Returns to normal when the engine switch is turned off) - Does not blink C If overcurrent is detected in the audio and visual system, system operation is disabled while the engine switch on (IG) (Returns to normal when the engine switch is turned off)

      The combination meter assembly cannot be turned off (short between IG12 and +B)

      Communication error DTCs may be stored due to short between AC42 and +B

      Tech Tips

      Varies depending on the number of times an open occurs in the +B circuit

      Converter circuit malfunction


      • Short between IG12 and +B

      • Short between AC42 and +B

      		 - - Does not blink B The converter cannot shut off the power source when the engine switch is turned off

      Engine switch does not turn on (ACC) (short between ACC and +B)

      Engine switch does not turn off (short between IG1 or IG2 and +B)

      Engine stop and start ECU power source circuit malfunction


      • Short between ACC and +B

      • Short between IG1 and +B

      • Short between IG2 and +B

      		 - - Does not blink B

      • Engine switch does not turn on(ACC)

      • Engine switch does not turn off

    A

    GO TO DTC CHART Click here

    C

    CHECK AUDIO AND VISUAL SYSTEM Click here

    B

  2. CHECK HARNESS AND CONNECTOR (POWER SOURCE)


    1. B001NRWE02
      Text in Illustration
      *a

      Front view of wire harness connector:

      (to Engine Stop and Start ECU)

      Disconnect the A76 and H191 engine stop and start ECU connectors.

    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      A76-1 (BIN2) - Body ground Always 9.5 to 14 V
      A76-3 (BIN1) - Body ground Always 9.5 to 14 V

    3. Turn the engine switch on (ACC).

    4. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      H191-19 (ACC) - Body ground Engine switch on (ACC) 9.5 to 14 V

    5. Turn the engine switch on (IG).

    6. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      H191-18 (IG2) - Body ground Engine switch on (IG) 9.5 to 14 V
      H191-21 (IG1) - Body ground Engine switch on (IG) 9.5 to 14 V

    7. Turn the headlight dimmer switch (light control switch) to the tail or head position.

    8. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      H191-20 (ILL) - Body ground Headlight dimmer switch (light control switch) in tail or head position 9.5 to 14 V

    9. Turn the engine switch off.

    10. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      H191-18 (IG2) - Body ground Engine switch off 0 to 1 V
      H191-19 (ACC) - Body ground Engine switch off 0 to 1 V
      H191-21 (IG1) - Body ground Engine switch off 0 to 1 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. CHECK HARNESS AND CONNECTOR (EACH SYSTEM - ENGINE STOP AND START ECU)


    1. Disconnect the H191 engine stop and start ECU connector.

    2. Disconnect the connector from the corresponding system ECU/sensor.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Skid Control ECU (Brake Actuator Assembly)
      Tester Connection Condition Specified Condition
      H191-1 (IG31) - A69-12 (IG1) Always Below 1 Ω
      H191-1 (IG31) - Body ground Always 10 kΩ or higher
      A69-12 (IG1) - Body ground Always 10 kΩ or higher
      Steering Sensor
      Tester Connection Condition Specified Condition
      H191-1 (IG31) - H23-4 (IG) Always Below 1 Ω
      H191-1 (IG31) - Body ground Always 10 kΩ or higher
      H23-4 (IG) - Body ground Always 10 kΩ or higher
      Combination Meter Assembly
      Tester Connection Condition Specified Condition
      H191-10 (IG12) - H14-21 (IG+) Always Below 1 Ω
      H191-10 (IG12) - Body ground Always 10 kΩ or higher
      H14-21 (IG+) - Body ground Always 10 kΩ or higher
      Power Steering ECU Assembly
      Tester Connection Condition Specified Condition
      H191-6 (IG11) - c1-1 (IG) Always Below 1 Ω
      H191-6 (IG11) - Body ground Always 10 kΩ or higher
      c1-1 (IG) - Body ground Always 10 kΩ or higher
      Multi-media Module Receiver Assembly
      Tester Connection Condition Specified Condition
      H191-15 (AC42) - H97-16 (ACC1) Always Below 1 Ω
      H191-15 (AC42) - Body ground Always 10 kΩ or higher
      H97-16 (ACC1) - Body ground Always 10 kΩ or higher
      H191-12 (B42) - H97-17 (+B1) Always Below 1 Ω
      H191-12 (B42) - Body ground Always 10 kΩ or higher
      H97-17 (+B1) - Body ground Always 10 kΩ or higher
      Radio Receiver Assembly
      Tester Connection Condition Specified Condition
      H191-15 (AC42) - H182-3 (ACC1) Always Below 1 Ω
      H191-15 (AC42) - Body ground Always 10 kΩ or higher
      H182-3 (ACC1) - Body ground Always 10 kΩ or higher
      H191-12 (B42) - H182-4 (+B1) Always Below 1 Ω
      H191-12 (B42) - Body ground Always 10 kΩ or higher
      H182-4 (+B1) - Body ground Always 10 kΩ or higher
      Multi-display Assembly
      Tester Connection Condition Specified Condition
      H191-15 (AC42) - H93-24 (ACC) Always Below 1 Ω
      H191-15 (AC42) - Body ground Always 10 kΩ or higher
      H93-24 (ACC) - Body ground Always 10 kΩ or higher
      H191-11 (B43) - H93-12 (B) Always Below 1 Ω
      H191-11 (B43) - Body ground Always 10 kΩ or higher
      H93-12 (B) - Body ground Always 10 kΩ or higher
      Telematics Transceiver
      Tester Connection Condition Specified Condition
      H191-16 (B12) - H101-1 (+B) Always Below 1 Ω
      H191-16 (B12) - Body ground Always 10 kΩ or higher
      H101-1 (+B) - Body ground Always 10 kΩ or higher
      H191-26 (IG13) - H101-7 (IG2) Always Below 1 Ω
      H191-26 (IG13) - Body ground Always 10 kΩ or higher
      H101-7 (IG2) - Body ground Always 10 kΩ or higher
      H191-24 (AC41) - H101-8 (ACC) Always Below 1 Ω
      H191-24 (AC41) - Body ground Always 10 kΩ or higher
      H101-8 (ACC) - Body ground Always 10 kΩ or higher
      Remote Touch (Remote Operation Board)
      Tester Connection Condition Specified Condition
      H191-24 (AC41) - H95-2 (ACC) Always Below 1 Ω
      H191-24 (AC41) - Body ground Always 10 kΩ or higher
      H95-2 (ACC) - Body ground Always 10 kΩ or higher
      H191-11 (B43) - H95-1 (+B)*1 Always Below 1 Ω
      H191-11 (B43) - Body ground*1 Always 10 kΩ or higher
      H95-1 (+B) - Body ground*1 Always 10 kΩ or higher
      H191-25 (IL41) - H95-1 (ILL+)*2 Always Below 1 Ω
      H191-25 (IL41) - Body ground*2 Always 10 kΩ or higher
      H95-1 (ILL+) - Body ground*2 Always 10 kΩ or higher
      H191-25 (IL41) - H95-9 (ILL+)*1 Always Below 1 Ω
      H191-25 (IL41) - Body ground*1 Always 10 kΩ or higher
      H95-9 (ILL+) - Body ground*1 Always 10 kΩ or higher
      Rear Control Switch
      Tester Connection Condition Specified Condition
      H191-25 (IL41) - h2-8 Always Below 1 Ω
      H191-25 (IL41) - Body ground Always 10 kΩ or higher
      h2-8 - Body ground Always 10 kΩ or higher
      H191-2 (B41) - h2-1 Always Below 1 Ω
      H191-2 (B41) - Body ground Always 10 kΩ or higher
      h2-1 - Body ground Always 10 kΩ or higher
      H191-3 (IG41) - h2-7 Always Below 1 Ω
      H191-3 (IG41) - Body ground Always 10 kΩ or higher
      h2-7 - Body ground Always 10 kΩ or higher
      Roof Console Box
      Tester Connection Condition Specified Condition
      H191-2 (B41) - T10-4 (+B1) Always Below 1 Ω
      H191-2 (B41) - T10-5 (+B5) Always Below 1 Ω
      H191-2 (B41) - Body ground Always 10 kΩ or higher
      T10-4 (+B1) - Body ground Always 10 kΩ or higher
      T10-5 (+B5) - Body ground Always 10 kΩ or higher
      Door Control and Tire Pressure Monitoring System Receiver Assembly
      Tester Connection Condition Specified Condition
      H191-2 (B41) - P29-7 (+B) Always Below 1 Ω
      H191-2 (B41) - Body ground Always 10 kΩ or higher
      P29-7 (+B) - Body ground Always 10 kΩ or higher
      H191-3 (IG41) - P29-1 (IG) Always Below 1 Ω
      H191-3 (IG41) - Body ground Always 10 kΩ or higher
      P29-1 (IG) - Body ground Always 10 kΩ or higher
      FR FOG Relay
      Tester Connection Condition Specified Condition
      H191-2 (B41) - FR FOG relay terminal 5 Always Below 1 Ω
      H191-2 (B41) - Body ground Always 10 kΩ or higher
      FR FOG relay terminal 5 - Body ground Always 10 kΩ or higher
      Foward Recognition Camera
      Tester Connection Condition Specified Condition
      H191-3 (IG41) - T12-7 (IGB) Always Below 1 Ω
      H191-3 (IG41) - Body ground Always 10 kΩ or higher
      T12-7 (IGB) - Body ground Always 10 kΩ or higher
      Inner Rear View Mirror Assembly
      Tester Connection Condition Specified Condition
      H191-3 (IG41) - T2-1 (IG)*4 Always Below 1 Ω
      H191-3 (IG41) - T15-1 (IG)*3 Always Below 1 Ω
      H191-3 (IG41) - Body ground Always 10 kΩ or higher
      T2-1 (IG) - Body ground*4 Always 10 kΩ or higher
      T15-1 (IG) - Body ground*3 Always 10 kΩ or higher
      Blind Spot Monitor Sensor LH
      Tester Connection Condition Specified Condition
      H191-3 (IG41) - U8-5 (BLB) Always Below 1 Ω
      H191-3 (IG41) - Body ground Always 10 kΩ or higher
      U8-5 (BLB) - Body ground Always 10 kΩ or higher
      Blind Spot Monitor Sensor RH
      Tester Connection Condition Specified Condition
      H191-3 (IG41) - U9-5 (BRB) Always Below 1 Ω
      H191-3 (IG41) - Body ground Always 10 kΩ or higher
      U9-5 (BRB) - Body ground Always 10 kΩ or higher
      Network Gateway ECU
      Tester Connection Condition Specified Condition
      H191-3 (IG41) - H193-11 (IG1) Always Below 1 Ω
      H191-3 (IG41) - Body ground Always 10 kΩ or higher
      H193-11 (IG1) - Body ground Always 10 kΩ or higher
      Millimeter Wave Radar Sensor Assembly
      Tester Connection Condition Specified Condition
      H191-3 (IG41) - A74-8 (IGB) Always Below 1 Ω
      H191-3 (IG41) - Body ground Always 10 kΩ or higher
      A74-8 (IGB) - Body ground Always 10 kΩ or higher
      Driving Support ECU Assembly
      Tester Connection Condition Specified Condition
      H191-3 (IG41) - H194-7 (B) Always Below 1 Ω
      H191-3 (IG41) - Body ground Always 10 kΩ or higher
      H194-7 (B) - Body ground Always 10 kΩ or higher

      • *1: w/ Navigation System

      • *2: w/o Navigation System

      • *3: w/ Pre-Crash Safety System

      • *4: w/o Pre-Crash Safety System


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. INSPECT ENGINE STOP AND START ECU (OUTPUT VOLTAGE FOR EACH SYSTEM)


    1. Disconnect the connector from the corresponding system ECU/sensor.

    2. Measure the voltage according to the value(s) in the table below.

      Tech Tips

      Measure the voltage at the corresponding terminals.

      Standard Voltage
      Tester Connection Condition Specified Condition
      H97-17 (+B1) - Body ground Always 10.5 to 16 V
      H182-4 (+B1) - Body ground Always 10.5 to 16 V
      H93-12 (B) - Body ground Always 10.5 to 16 V
      H101-1 (+B) - Body ground Always 10.5 to 16 V
      H95-1 (+B) - Body ground*1 Always 10.5 to 16 V
      h2-1 - Body ground Always 10.5 to 16 V
      T10-4 (+B1) - Body ground Always 10.5 to 16 V
      T10-5 (+B5) - Body ground Always 10.5 to 16 V
      P29-7 (+B) - Body ground*2 Always 10.5 to 16 V
      FR FOG relay terminal 5 - Body ground Always 10.5 to 16 V

      • *1: w/ Navigation System

      • *2: w/o Door Ajar Warning Buzzer Function

    3. Turn the engine switch on (ACC).

    4. Measure the voltage according to the value(s) in the table below.

      Tech Tips

      Measure the voltage at the corresponding terminals.

      Standard Voltage
      Tester Connection Condition Specified Condition
      H97-16 (ACC1) - Body ground Engine switch on (ACC) 10.5 to 16 V
      H182-3 (ACC1) - Body ground Engine switch on (ACC) 10.5 to 16 V
      H93-24 (ACC) - Body ground Engine switch on (ACC) 10.5 to 16 V
      H101-8 (ACC) - Body ground Engine switch on (ACC) 10.5 to 16 V
      H95-2 (ACC) - Body ground Engine switch on (ACC) 10.5 to 16 V

    5. Turn the engine switch on (IG).

    6. Measure the voltage according to the value(s) in the table below.

      Tech Tips

      Measure the voltage at the corresponding terminals.

      Standard Voltage
      Tester Connection Condition Specified Condition
      A69-12 (IG1) - Body ground Engine switch on (IG) 10.5 to 16 V
      H23-4 (IG) - Body ground Engine switch on (IG) 10.5 to 16 V
      H14-21 (IG+) - Body ground Engine switch on (IG) 10.5 to 16 V
      c1-1 (IG) - Body ground Engine switch on (IG) 10.5 to 16 V
      H101-7 (IG2) - Body ground Engine switch on (IG) 10.5 to 16 V
      h2-7 - Body ground Engine switch on (IG) 10.5 to 16 V
      P29-1 (IG) - Body ground Engine switch on (IG) 10.5 to 16 V
      P25-1 (IG) - Body ground Engine switch on (IG) 10.5 to 16 V
      T12-7 (IGB) - Body ground Engine switch on (IG) 10.5 to 16 V
      T2-1 (IG) - Body ground*1 Engine switch on (IG) 10.5 to 16 V
      T15-1 (IG) - Body ground*2 Engine switch on (IG) 10.5 to 16 V
      U8-5 (BLB) - Body ground Engine switch on (IG) 10.5 to 16 V
      U9-5 (BRB) - Body ground Engine switch on (IG) 10.5 to 16 V
      H193-11 (IG1) - Body ground Engine switch on (IG) 10.5 to 16 V
      A74-8 (IGB) - Body ground Engine switch on (IG) 10.5 to 16 V
      H194-7 (B) - Body ground Engine switch on (IG) 10.5 to 16 V

      • *1: w/ Pre-Crash Safety System

      • *2: w/o Pre-Crash Safety System

    7. Turn the headlight dimmer switch (light control switch) to the tail or head position.

    8. Measure the voltage according to the value(s) in the table below.

      Tech Tips

      Measure the voltage at the corresponding terminals.

      Standard Voltage
      Tester Connection Condition Specified Condition
      H95-1 (ILL+) - Body ground*1 Headlight dimmer switch (light control switch) in tail or head position 10.5 to 16 V
      H95-9 (ILL+) - Body ground*2 Headlight dimmer switch (light control switch) in tail or head position 10.5 to 16 V
      h2-8 - Body ground Headlight dimmer switch (light control switch) in tail or head position 10.5 to 16 V

      • *1: w/o Navigation System

      • *2: w/ Navigation System


    OK

    CHECK POWER SOURCE CIRCUIT (POWER SOURCE CIRCUIT OF RELATED SYSTEM))

    NG

    REPLACE ENGINE STOP AND START ECU Click here

  5. CHECK AUDIO AND VISUAL SYSTEM


    1. Turn the engine switch off and wait for 1 minute.

    2. Turn the engine switch on (IG).

    3. Lower the audio volume.

    4. Check if the audio and visual system operates normally.

      OK
      Audio and visual system operates normally.

    OK

    END

    NG

  6. CHECK EXTERNAL BACKUP BOOST CONVERTER (ECO RUN VEHICLE CONVERTER ASSEMBLY) ACO, BO1TERMINAL CIRCUIT


    1. Disconnect the A79 external backup boost converter (eco run vehicle converter assembly) connector.

    2. Disconnect the H99*1 or H87*2 stereo component amplifier assembly connector.


      • *1: w/ Navigation System

      • *2: w/o Navigation System

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      w/ Navigation System
      Tester Connection Condition Specified Condition
      A79-5 (BO1) - Body ground Always 10 kΩ or higher
      H99-1 (+B) - Body ground Always 10 kΩ or higher
      H99-16 (+B2) - Body ground Always 10 kΩ or higher
      w/o Navigation System
      Tester Connection Condition Specified Condition
      A79-12 (ACO) - Body ground Always 10 kΩ or higher
      H87-12 (ACC) - Body ground Always 10 kΩ or higher
      A79-5 (BO1) - Body ground Always 10 kΩ or higher
      H87-1 (+B) - Body ground Always 10 kΩ or higher
      H87-16 (+B2) - Body ground Always 10 kΩ or higher

    OK

    GO TO AUDIO AND VISUAL SYSTEM Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR