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STOP AND START SYSTEM Backup Boost Converter Circuit

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DTC Code DTC Name
  Backup Boost Converter Circuit
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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 navigation 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.

Tip:

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* 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.

*: A semiconductor fuse self-resets according to electric signals.


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WIRING DIAGRAM

Refer to DTC B22C0.

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CAUTION / NOTICE / HINT

Note:

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

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  • 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.

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  • 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.

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  • for Automatic Transmission:

    When the engine stop and start ECU is replaced, check the electromagnetic oil pump.

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

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PROCEDURE


  1. Click here

    CHECK PROBLEM SYMPTOMS


    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 Symptom Proceed to

      When the engine is restarted by stop and start control, the following symptoms may occur.


      • The audio and visual system is reset

      • The combination meter assembly fades out

      • Air conditioning system cannot be operated

      • Lane departure alert system cannot be operated

      • Pre-crash safety system cannot be operated

      • Road sign assist system cannot be operated

      Backup boost converter internal malfunction


      • Internal power source malfunction

      • Internal power source overvoltage

      • Duty error

      • Communication cycle error

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

      Systems on the converter output side do not operate

      B42 terminal:

      The audio and visual system will not function

      IG41 terminal: None of the following will operate


      • Air conditioning system

      • Lane departure Alert system

      • Pre-crash safety system

      • Road sign assist system

      • Systems whose power is supplied from the body ECU

      		 Overcurrent applied to an output terminal (output terminal relay circuit is shutoff)

      Stop and start control is prohibited

      (Connected ECUs or sensors may detect power source malfunction DTCs)

      		 B22C0 Blinks Systems do not operate as power supply from the converter is cut off A

      Systems do not operate

      (Due to converter input side malfunction)

      IG1 terminal: None of the following operate


      • Skid control ECU (brake actuator assembly)

      • Spiral with sensor cable sub-assembly

      • Air conditioning control assembly

      • Systems whose power is supplied from the body ECU

      IG2 terminal: The combination meter assembly will not function

      ACC terminal: The audio 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 blink (Blinks when communication error DTCs are stored) Systems do not operate as power supply from the converter is cut off B

      Systems on the converter output side do not operate

      (varies depending on the malfunctioning relay circuit the converter detected)

      AC42 terminal: The audio and visual system will not function

      IG12 terminal: The combination meter assembly will not function

      Malfunction in circuits the converter supplies power to

      (between the 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) Systems do not operate as power supply from the converter is cut off B

      All of the following will operate


      • Radio and display receiver assembly

      • Skid control ECU (brake actuator assembly)

      • Spiral with sensor cable sub-assembly

      • Combination meter assembly

      • Air conditioning control assembly

      • Millimeter wave radar sensor assembly

      • Forward recognition camera

      • Systems whose power is supplied from the body ECU

      • 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) All systems that the converter supplies power to do not operate (see circuit diagram) A
      P323B

      The audio 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 navigation system (Returns to normal when the ignition switch is turned off) - Does not blink

      If overcurrent is detected in the navigation system, system operation is disabled while the ignition switch is ON

      (Returns to normal when the ignition switch is turned off)

      		 C

      The audio and visual system cannot be turned off (short between AC42 and +B)

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

      Communication error DTCs may be stored due to short between IG31 and +B

      Tip:

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

      Converter circuit malfunction


      • Short between AC42 and +B

      • Short between IG31 and +B

      • Short between IG12 and +B

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

      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

      • Ignition switch does not turn to ACC

      • Ignition switch does not turn off

      		 B
      Result
      Proceed to
      A
      B
      C

  2. Click here

    CHECK ENGINE STOP AND START ECU (POWER SOURCE CIRCUIT)


    1. A01SH05C07
      *a

      Front view of wire harness connector

      (to Engine Stop and Start ECU)

      Disconnect the G125 and G127 engine stop and start ECU connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      G125-1 (BIN2) - Body ground Always 9.5 to 14 V
      G125-3 (BIN1) - Body ground Always 9.5 to 14 V

    3. Turn the ignition switch to ACC.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      G127-19 (ACC) - Body ground Ignition switch ACC 9.5 to 14 V

    5. Turn the ignition switch to ON.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      G127-21 (IG1) - Body ground Ignition switch ON 9.5 to 14 V
      G127-18 (IG2) - Body ground Ignition switch ON 9.5 to 14 V

    7. Turn the ignition switch off.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      G127-21 (IG1) - Body ground Ignition switch off 0 to 1 V
      G127-19 (ACC) - Body ground Ignition switch off 0 to 1 V
      G127-18 (IG2) - Body ground Ignition switch off 0 to 1 V
      Result
      Proceed to
      OK
      NG

    • OKClick here
    • NG

      REPAIR OR REPLACE HARNESS OR CONNECTOR

  3. Click here

    CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - EACH ECU OR SENSOR)


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

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

      Standard Resistance
      Table 1. Radio and Display Receiver Assembly
      Tester Connection Condition Specified Condition
      G127-12 (B42) - G40-4 (+B1) Always Below 1 Ω
      G127-15 (AC42) - G40-3 (ACC1) Always Below 1 Ω
      G127-12 (B42) - Body ground Always 10 kΩ or higher
      G127-15 (AC42) - Body ground Always 10 kΩ or higher
      G40-4 (+B1) - Body ground Always 10 kΩ or higher
      G40-3 (ACC1) - Body ground Always 10 kΩ or higher
      Table 2. Skid Control ECU (Brake Actuator Assembly)
      Tester Connection Condition Specified Condition
      G127-1 (IG31) - A4-12 (IG1) Always Below 1 Ω
      G127-1 (IG31) - Body ground Always 10 kΩ or higher
      A4-12 (IG1) - Body ground Always 10 kΩ or higher
      Table 3. Spiral with Sensor Cable Sub-assembly
      Tester Connection Condition Specified Condition
      G127-1 (IG31) - G21-4 (IG) Always Below 1 Ω
      G127-1 (IG31) - Body ground Always 10 kΩ or higher
      G21-4 (IG) - Body ground Always 10 kΩ or higher
      Table 4. Combination Meter Assembly
      Tester Connection Condition Specified Condition
      G127-10 (IG12) - G9-22 (IG+) Always Below 1 Ω
      G127-10 (IG12) - Body ground Always 10 kΩ or higher
      G9-22 (IG+) - Body ground Always 10 kΩ or higher
      Table 5. Air Conditioning Control Assembly
      Tester Connection Condition Specified Condition
      G127-3 (IG41) - G32-2 (IG+) Always Below 1 Ω
      G127-3 (IG41) - Body ground Always 10 kΩ or higher
      G32-2 (IG+) - Body ground Always 10 kΩ or higher
      Table 6. Millimeter Wave Radar Sensor Assembly
      Tester Connection Condition Specified Condition
      G127-3 (IG41) - A64-8 (IGB) Always Below 1 Ω
      G127-3 (IG41) - Body ground Always 10 kΩ or higher
      A64-8 (IGB) - Body ground Always 10 kΩ or higher
      Table 7. Forward Recognition Camera
      Tester Connection Condition Specified Condition
      G127-3 (IG41) - Q4-7 (IGB) Always Below 1 Ω
      G127-3 (IG41) - Body ground Always 10 kΩ or higher
      Q4-7 (IGB) - Body ground Always 10 kΩ or higher
      Table 8. Instrument Panel Junction Block Assembly (Body ECU)
      Tester Connection Condition Specified Condition
      G127-3 (IG41) - 2D-5 Always Below 1 Ω
      G127-3 (IG41) - Body ground Always 10 kΩ or higher
      2D-5 - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    • OKClick here
    • NG

      REPAIR OR REPLACE HARNESS OR CONNECTOR

  4. Click here

    CHECK ENGINE STOP AND START ECU (EACH ECU OR SENSOR POWER SOURCE CIRCUIT)


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

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

      Tip:

      Measure the voltage at the corresponding terminals.

      Standard Voltage
      Tester Connection Condition Specified Condition
      G40-4 (+B1) - Body ground Always 10.5 to 16 V

    3. Turn the ignition switch to ACC.

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

      Tip:

      Measure the voltage at the corresponding terminals.

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      G40-3 (ACC1) - Body ground Ignition switch ACC 10.5 to 16 V

    5. Turn the ignition switch to ON.

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

      Tip:

      Measure the voltage at the corresponding terminals.

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      G21-4 (IG) - Body ground Ignition switch ON 10.5 to 16 V
      A4-12 (IG1) - Body ground Ignition switch ON 10.5 to 16 V
      G9-22 (IG+) - Body ground Ignition switch ON 10.5 to 16 V
      G32-2 (IG+) - Body ground Ignition switch ON 10.5 to 16 V
      A64-8 (IGB) - Body ground Ignition switch ON 10.5 to 16 V
      Q4-7 (IGB) - Body ground Ignition switch ON 10.5 to 16 V
      2D-5 - Body ground Ignition switch ON 10.5 to 16 V
      Result
      Proceed to
      OK
      NG

    • OK

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

    • NG

      REPLACE ENGINE STOP AND START ECUClick here

  5. Click here

    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.
      Result
      Proceed to
      NG
      OK

  6. Click here

    CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - RADIO AND DISPLAY RECEIVER ASSEMBLY)


    1. Disconnect the G127 engine stop and start ECU connector.

    2. Disconnect the G40 radio and display receiver assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      G127-12 (B42) - Body ground Always 10 kΩ or higher
      G40-4 (+B1) - Body ground Always 10 kΩ or higher
      G127-15 (AC42) - Body ground Always 10 kΩ or higher
      G40-3 (ACC1) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    • OK

      GO TO AUDIO AND VISUAL SYSTEMClick here

    • NG

      REPAIR OR REPLACE HARNESS OR CONNECTOR