STOP AND START SYSTEM Backup Boost Converter Circuit

DTC Code DTC Name
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.

The backup boost converter 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.

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 (circuit will remain shut off until next trip).

When an 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)

  • Vehicle stability control system

  • Power steering system

  • Meter/gauge system

  • Audio and visual system

  • Automatic air conditioning system

WIRING DIAGRAM

Refer to DTC B22C0.

Click here

CAUTION / NOTICE / HINT

Note:

  • Before replacing the engine stop and start ECU, download the current status (number of starter operations) and upload it into a new engine stop and start ECU.

    Click here

  • After replacing the engine stop and start ECU or air conditioning control assembly, initialize 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 procedure.

PROCEDURE

  1. 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 resets

      • The combination meter assembly fades 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 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

      BO1 terminal: The audio and visual system and automatic air conditioning system will not function

      IGO1 terminal: All of the following will not operate:

      • Vehicle stability control system

      • Power steering system

      • Systems whose power is supplied from the main body ECU (multiplex network 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: All of the following will not operate:

      • Vehicle stability control system

      • Power steering system

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

      IG2 terminal: The combination meter assembly will not function

      ACC terminal: The audio will not operate

      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

      (systems vary depending on the malfunctioning circuit the converter detected)

      ACO terminal: The audio and visual system will not operate

      IGO2 terminal: The combination meter assembly will not operate

      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 systems do not operate:

      • Vehicle stability control system

      • Power steering system

      • Meter/gauge system

      • Audio and visual system

      • Automatic air conditioning system

      • Systems whose power is supplied from the main body ECU (multiplex network 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 and visual system does not operate

      (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

      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)

      C

      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

      Tip:

      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

      The converter cannot shut off the 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
    A

    GO TO DTC CHART

    Click hereClick hereClick here

    C

    CHECK AUDIO AND VISUAL SYSTEMClick here

    B

  2. CHECK ENGINE STOP AND START ECU (POWER SOURCE CIRCUIT)

    1. A285704C22

      *a

      Front view of wire harness connector:

      (to Engine Stop and Start ECU)

      Disconnect the A23 and A25 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

      A23-7 (BIN) - 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

      Condition

      Specified Condition

      A25-19 (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

      Condition

      Specified Condition

      A25-17 (IG1) - Body ground

      Ignition switch ON

      9.5 to 14 V

      A25-20 (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

      Condition

      Specified Condition

      A25-17 (IG1) - Body ground

      Ignition switch off

      0 to 1 V

      A25-19 (ACC) - Body ground

      Ignition switch off

      0 to 1 V

      A25-20 (IG2) - Body ground

      Ignition switch off

      0 to 1 V

    Result

    Proceed to

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. 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 (for Radio and Display Receiver Assembly Type)

      Tester Connection

      Condition

      Specified Condition

      A25-2 (BO1) - E31-4 (+B1)

      Always

      Below 1 Ω

      A25-3 (ACO) - E31-3 (ACC1)

      Always

      Below 1 Ω

      A25-2 (BO1) - Body ground

      Always

      10 kΩ or higher

      A25-3 (ACO) - Body ground

      Always

      10 kΩ or higher

      E31-4 (+B1) - Body ground

      Always

      10 kΩ or higher

      E31-3 (ACC1) - Body ground

      Always

      10 kΩ or higher
      Table 2. Radio Receiver Assembly (for Radio Receiver Assembly Type)

      Tester Connection

      Condition

      Specified Condition

      A25-2 (BO1) - E53-4 (+B1)

      Always

      Below 1 Ω

      A25-3 (ACO) - E53-3 (ACC1)

      Always

      Below 1 Ω

      A25-2 (BO1) - Body ground

      Always

      10 kΩ or higher

      A25-3 (ACO) - Body ground

      Always

      10 kΩ or higher

      E53-4 (+B1) - Body ground

      Always

      10 kΩ or higher

      E53-3 (ACC1) - Body ground

      Always

      10 kΩ or higher
      Table 3. Air Conditioning Control Assembly (for Automatic Air Conditioning System)

      Tester Connection

      Condition

      Specified Condition

      A25-2 (BO1) - E54-7 (B)

      Always

      Below 1 Ω

      A25-2 (BO1) - Body ground

      Always

      10 kΩ or higher

      E54-7 (B) - Body ground

      Always

      10 kΩ or higher
      Table 4. Skid Control ECU (Brake Actuator Assembly)

      Tester Connection

      Condition

      Specified Condition

      A25-12 (IGO1) - A39-28 (IG1)

      Always

      Below 1 Ω

      A25-12 (IGO1) - Body ground

      Always

      10 kΩ or higher

      A39-28 (IG1) - Body ground

      Always

      10 kΩ or higher
      Table 5. Spiral with Sensor Cable Sub-assembly

      Tester Connection

      Condition

      Specified Condition

      A25-12 (IGO1) - E15-5 (IG)

      Always

      Below 1 Ω

      A25-12 (IGO1) - Body ground

      Always

      10 kΩ or higher

      E15-5 (IG) - Body ground

      Always

      10 kΩ or higher
      Table 6. Power Steering ECU Assembly

      Tester Connection

      Condition

      Specified Condition

      A25-12 (IGO1) - E5-1 (IG)

      Always

      Below 1 Ω

      A25-12 (IGO1) - Body ground

      Always

      10 kΩ or higher

      E5-1 (IG) - Body ground

      Always

      10 kΩ or higher
      Table 7. Combination Meter Assembly

      Tester Connection

      Condition

      Specified Condition

      A25-11 (IGO2) - E12-39 (IG+)

      Always

      Below 1 Ω

      A25-11 (IGO2) - Body ground

      Always

      10 kΩ or higher

      E12-39 (IG+) - Body ground

      Always

      10 kΩ or higher
      Table 8. Main Body ECU (Multiplex Network Body ECU)

      Tester Connection

      Condition

      Specified Condition

      A25-12 (IGO1) - 3D-4

      Always

      Below 1 Ω

      A25-12 (IGO1) - Body ground

      Always

      10 kΩ or higher

      3D-4 - Body ground

      Always

      10 kΩ or higher

    Result

    Proceed to

    OK

    NG
    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

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

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

      A325918C01

      *A

      for Automatic Air Conditioning System

      *B

      for Radio and Display Receiver Assembly Type

      *C

      for Radio Receiver Assembly Type

      -

      -

      *a

      Front view of wire harness connector

      (to Main Body ECU (Multiplex Network Body ECU))

      *b

      Front view of wire harness connector

      (to Power Steering ECU Assembly)

      *c

      Front view of wire harness connector

      (to Spiral with Sensor Cable Sub-assembly)

      *d

      Front view of wire harness connector

      (to Combination Meter Assembly)

      *e

      Front view of wire harness connector

      (to Skid Control ECU (Brake Actuator Assembly)

      *f

      Front view of wire harness connector

      (to Air Conditioning Control Assembly)

      *g

      Front view of wire harness connector

      (to Radio and Display Receiver Assembly)

      *h

      Front view of wire harness connector

      (to Radio Receiver Assembly)

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

      Tip:

      Measure the voltage at the corresponding terminals.

      Standard Voltage

      Table 9. Radio and Display Receiver Assembly (for Radio and Display Receiver Assembly Type)

      Tester Connection

      Condition

      Specified Condition

      E31-4 (+B1) - Body ground

      Always

      9.5 to 14 V
      Table 10. Radio Receiver Assembly (for Radio Receiver Assembly Type)

      Tester Connection

      Condition

      Specified Condition

      E53-4 (+B1) - Body ground

      Always

      9.5 to 14 V
      Table 11. Air Conditioning Control Assembly (for Automatic Air Conditioning System)

      Tester Connection

      Condition

      Specified Condition

      E54-7 (B) - 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.

      Tip:

      Measure the voltage at the corresponding terminals.

      Standard Voltage

      Table 12. Radio and Display Receiver Assembly (for Radio and Display Receiver Assembly Type)

      Tester Connection

      Condition

      Specified Condition

      E31-3 (ACC1) - Body ground

      Ignition switch ACC

      9.5 to 14 V
      Table 13. Radio Receiver Assembly (for Radio Receiver Assembly Type)

      Tester Connection

      Condition

      Specified Condition

      E53-3 (ACC1) - 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.

      Tip:

      Measure the voltage at the corresponding terminals.

      Standard Voltage

      Tester Connection

      Condition

      Specified Condition

      A39-28 (IG1) - Body ground

      Ignition switch ON

      9.5 to 14 V

      E12-39 (IG+) - Body ground

      Ignition switch ON

      9.5 to 14 V

      E15-5 (IG) - Body ground

      Ignition switch ON

      9.5 to 14 V

      E5-1 (IG) - Body ground

      Ignition switch ON

      9.5 to 14 V

      3D-4 - Body ground

      Ignition switch ON

      9.5 to 14 V

    Result

    Proceed to

    OK

    NG
    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.

    Result

    Result

    Proceed to

    NG

    A

    OK

    B
    B

    END

    A

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

    1. Disconnect the A25 engine stop and start ECU connector.

    2. Disconnect the E31 radio and display receiver assembly*1 or E53 radio receiver assembly*2 connector.

      • *1: for Radio and Display Receiver Assembly Type

      • *2: for Radio Receiver Assembly Type

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      A25-2 (BO1) - Body ground

      Always

      10 kΩ or higher

      E31-4 (+B1) - Body ground*1

      Always

      10 kΩ or higher

      E53-4 (+B1) - Body ground*2

      Always

      10 kΩ or higher

      A25-3 (ACO) - Body ground

      Always

      10 kΩ or higher

      E31-3 (ACC1) - Body ground*1

      Always

      10 kΩ or higher

      E53-3 (ACC1) - Body ground*2

      Always

      10 kΩ or higher

      • *1: for Radio and Display Receiver Assembly Type

      • *2: for Radio Receiver Assembly Type

      Result

      Result

      Proceed to

      OK (Radio and Display Receiver Assembly Type)

      A

      OK (for Radio Receiver Assembly 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