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 helps maintain the power source voltage when the engine is restarted by stop and start control.

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

If a DTC is output, troubleshoot the DTC first.

Tech Tips

A relay function and fuse function are provided in the backup boost converter.

If there is a malfunction in any of the electrical system circuits connected to the 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*1 when the ignition 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 ignition switch is turned to ON.

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


    The backup boost converter supplies power to:

  • Main body ECU (multiplex network body ECU)

  • VSC system

  • Power steering system

  • Meter/gauge system

  • Tire pressure warning 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 control 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.


      • The combination meter 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

      • Duty error

      • Communication cycle error

      		 Stop and start system control prohibited P323B Blinks A Converter output voltage cannot be boosted when the engine is restarted
      Battery voltage drop

      Systems on the converter output side do not operate

      BO1 terminal: All of the following will not function

      IGO1 terminal : All of the following will not operate


      • VSC system

      • Power steering system

      • Systems whose power is supplied from the main body ECU (multiplex network body)

        Tire pressure warning 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)

      IG1 terminal: All of the following do not operate


      • VSC system

      • Power steering system

      • Meter/gauge system

      • Tire pressure warning system

      IG2 terminal: The combination meter assembly will not function

      ACC terminal: The audio and visual system will not function

      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)

      ACO terminal: The audio and visual system will not function

      IGO2 terminal: the combination meter assembly 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


      • VSC system

      • Power steering system

      • Meter/ gauge system

      • Audio and visual system

      • Tire pressure warning system

      • Open in BBC fuse circuit

      • Short in converter circuit

      • Backup boost converter malfunction

      		 Stop and start control prohibited

      • P0617

      • P323B

      		 Does not blink (Due to disabled meter/gauge system) A All systems that the converter supplies power to do not operate (see circuit diagram)
      The audio and visual system does not function (until the ignition switch is turned off) Excessive audio volume Data List item "State of BBC" displays "BBC Overcurrent" 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 ignition switch is turned off) - Does not blink C If overcurrent is detected in the audio and visual system, system operation is disabled while the ignition switch is on (Returns to normal when the ignition switch is turned off)

      The audio and visual system cannot be turned off (short between ACO and +B)

      The combination meter assembly cannot be turned off (short between IGO2 and +B)

      Communication error DTCs may be stored due to short between IGO1 and +B

      Tech Tips

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

      Converter circuit malfunction


      • Short between ACO and +B

      • Short between IGO1 and +B

      • Short between IGO2 and +B

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

      Ignition switch does not turn to ACC (short between ACC and +B)

      Ignition 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

      • Ignition switch does not turn to ACC

      • Ignition 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. A01VHFUE01
      Text in Illustration
      *a

      Front view of wire harness connector:

      (to Engine Stop and Start ECU)

      Disconnect the 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
      A91-7 (BIN) - body ground Always 9.5 to 14 V

    3. Turn the ignition switch to ON.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      F131-17 (IG1) - Body ground Ignition switch ON 9.5 to 14 V
      F131-19 (ACC) - Body ground Ignition switch ON 9.5 to 14 V
      F131-20 (IG2) - Body ground Ignition switch ON 9.5 to 14 V

    5. Turn the ignition switch off.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      F131-17 (IG1) - Body ground Ignition switch off 0 to 1 V
      F131-19 (ACC) - Body ground Ignition switch off 0 to 1 V
      F131-20 (IG2) - Body ground Ignition 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 F131 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 (for Radio and Display Receiver Type)
      Tester Connection Condition Specified Condition
      F131-2 (BO1) - F113-4 (+B1) Always Below 1 Ω
      F131-3 (ACO) - F113-3 (ACC1) Always Below 1 Ω
      F131-2 (BO1) or F113-4 (+B1) - Body ground Always 10 kΩ or higher
      F131-3 (ACO) or F113-3 (ACC1) - Body ground Always 10 kΩ or higher
      Standard Resistance (for Radio Receiver Type)
      Tester Connection Condition Specified Condition
      F131-2 (BO1) - F45-4 (+B1) Always Below 1 Ω
      F131-3 (ACO) - F45-3 (ACC1) Always Below 1 Ω
      F131-2 (BO1) or F45-4 (+B1) - Body ground Always 10 kΩ or higher
      F131-3 (ACO) or F45-3 (ACC1) - Body ground Always 10 kΩ or higher
      Standard Resistance (for Skid Control ECU (Brake Actuator Assembly))
      Tester Connection Condition Specified Condition
      F131-12 (IGO1) - A78-20 (IG1)*1 Always Below 1 Ω
      F131-12 (IGO1) - A79-20 (IG1)*2 Always Below 1 Ω
      F131-12 (IGO1) or A78-20 (IG1)*1 - Body ground Always 10 kΩ or higher
      F131-12 (IGO1) or A79-20 (IG1)*2 - Body ground Always 10 kΩ or higher

      • *1: for LHD with CVT, and RHD

      • *2: for LHD except CVT

      Standard Resistance (for Spiral with Sensor Cable Sub-assembly)
      Tester Connection Condition Specified Condition
      F131-12 (IGO1) - F30-5 (IG) Always Below 1 Ω
      F131-12 (IGO1) or F30-5 (IG) - Body ground Always 10 kΩ or higher
      Standard Resistance (for Power Steering ECU Assembly)
      Tester Connection Condition Specified Condition
      F131-12 (IGO1) - F6-1 (IG) Always Below 1 Ω
      F131-12 (IGO1) or F6-1 (IG) - Body ground Always 10 kΩ or higher
      Standard Resistance (for Combination Meter Assembly)
      Tester Connection Condition Specified Condition
      F131-11 (IGO2) - F1-39 (IG+) Always Below 1 Ω
      F131-11 (IGO2) or F1-39 (IG+) - Body ground Always 10 kΩ or higher
      Standard Resistance (for Main Body ECU (multiplex network body ECU))
      Tester Connection Condition Specified Condition
      F131-12 (IGO1) - 3A-40 (IG) Always Below 1 Ω
      F131-12 (IGO1) or 3A-40 (IG) - Body ground Always 10 kΩ or higher

    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. Turn the ignition switch to ON.

      A01VF0UE02
      Text in Illustration
      *A for Radio and Display Receiver Type *B for Radio Receiver Type
      *C for LHD with CVT, and RHD *D for LHD except CVT
      *a

      Front view of wire harness connector:

      (to Skid Control ECU (Brake Actuator Assembly))

      		 *b

      Front view of wire harness connector:

      (to Combination Meter Assembly)
      *c

      Front view of wire harness connector:

      (to Tire pressure warning ECU and receiver)

      		 *d

      Front view of wire harness connector:

      (to Main Body ECU (multiplex network body ECU))
      *e

      Front view of wire harness connector:

      (to Radio and Display Receiver Assembly)

      		 *f

      Front view of wire harness connector:

      (to Radio Receiver Assembly)
      *g

      Front view of wire harness connector:

      (to Spiral with Sensor Cable Sub-assembly)

      		 *h

      Front view of wire harness connector:

      (to Power Steering ECU Assembly)

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

      Tech Tips

      Measure the voltage at the corresponding terminals.

      Standard Voltage
      for Radio and Display Receiver Type
      Tester Connection Condition Specified Condition
      F113-4 (+B1) - Body ground Always 9.5 to 14 V
      for Radio Receiver Type
      Tester Connection Condition Specified Condition
      F45-4 (+B1) - Body ground Always 9.5 to 14 V

    4. Turn the ignition switch to ACC.

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

      Tech Tips

      Measure the voltage at the corresponding terminals.

      Standard Voltage
      for Radio and Display Receiver Type
      Tester Connection Condition Specified Condition
      F113-3 (ACC1) - Body ground Always 9.5 to 14 V
      for Radio Receiver Type
      Tester Connection Condition Specified Condition
      F45-3 (ACC1) - Body ground Always 9.5 to 14 V

    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 Switch Condition Specified Condition
      F113-4 (+B1)*1 - Body ground Always 9.5 to 14 V
      F113-3 (ACC1)*1 - Body ground Ignition switch ACC 9.5 to 14 V
      F45-4 (+B1)*2 - Body ground Always 9.5 to 14 V
      F45-3 (ACC1)*2 - Body ground Ignition switch ACC 9.5 to 14 V
      A78-20 (IG1)*3 - Body ground Ignition switch ON 9.5 to 14 V
      A79-20 (IG1)*4 - Body ground Ignition switch ON 9.5 to 14 V
      F1-39 (IG+) - Body ground Ignition switch ON 9.5 to 14 V
      F30-5 (IG) - Body ground Ignition switch ON 9.5 to 14 V
      F6-1 (IG) - Body ground Ignition switch ON 9.5 to 14 V
      3A-40 (IG) - Body ground Ignition switch ON 9.5 to 14 V

      • *1: for Radio and Display Receive Type

      • *2: for Radio Receiver Type

      • *3: for LHD with CVT, and RHD

      • *4: for LHD except CVT


    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 ignition switch off and wait for 1 minute.

    2. Turn the ignition switch to ON.

    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 HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - OPTION CONNECTOR)


    1. Disconnect the F131 engine stop and start ECU connector.

    2. Disconnect the F113 radio and display receiver assembly connector. (for Radio and Display Receive Type)

    3. Disconnect the F45 radio receiver assembly connector. (for Radio Receiver Type)

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

      Standard Resistance
      for Radio and Display Receiver Type
      Tester Connection Condition Specified Condition
      F131-2 (BO1) or F113-4 (+B1) - Body ground Always 10 kΩ or higher
      F131-3 (ACO) or F113-3 (ACC1) - Body ground Always 10 kΩ or higher
      for Radio Receiver Type
      Tester Connection Condition Specified Condition
      F131-2 (BO1) or F45-4 (+B1) - Body ground Always 10 kΩ or higher
      F131-3 (ACO) or F45-3 (ACC1) - Body ground Always 10 kΩ or higher
      Result
      Result Proceed to
      OK (for Radio and Display Receiver Type) A
      OK (for Radio Receiver Type) B
      NG C

    A

    GO TO AUDIO AND VISUAL SYSTEM Click here

    B

    GO TO AUDIO AND VISUAL SYSTEM Click here

    C

    REPAIR OR REPLACE HARNESS OR CONNECTOR