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.

This prevents various functions such as the audio and visual system or 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.

Backup boost converter supplies power to:

  • Vehicle stability control system

  • Power steering system

  • Meter/gauge system

  • Audio and visual system or navigation system

  • Automatic glare-resistant EC mirror

  • TOYOTA parking assist-sensor system

  • Tire pressure warning system

WIRING DIAGRAM

Refer to DTC 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 yaw rate sensor, 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 or navigation system is reset

      • 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

      • 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

      BO1 terminal: The audio and visual system or navigation system will not function

      IGO1 terminal: All of the following will not operate

      • Vehicle stability control system

      • Power steering system

      • Automatic glare-resistant EC mirror

      • TOYOTA parking assist-sensor system

      • Tire pressure warning system

      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 do not operate

      • Vehicle stability control system

      • Power steering system

      • TOYOTA parking assist-sensor system

      • Automatic glare-resistant EC mirror

      • Tire pressure warning system

      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)

      ACO terminal: The audio and visual system or navigation system will not function

      IGO2 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

      • Audio and visual system or navigation system

      • Vehicle stability control system

      • Power steering system

      • TOYOTA parking assist-sensor system

      • Meter/gauge system

      • Automatic glare-resistant EC mirror

      • Tire pressure warning 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)

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

      A

      P323B

      The audio and visual system or navigation 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 or navigation system (Returns to normal when the ignition switch is turned off)

      -

      Does not blink

      If overcurrent is detected in the audio and visual system or 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 or navigation 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 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

    GO TO DIAGNOSTIC TROUBLE CODE CHART

    (Click here)

    CHECK AUDIO AND VISUAL SYSTEM OR NAVIGATION SYSTEMClick here

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

    1. U122081E02

      Disconnect the A73 and H121 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

      A73-7 (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

      Switch Condition

      Specified Condition

      H121-19 (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

      H121-17 (IG1) - Body ground

      Ignition switch ON

      9.5 to 14 V

      H121-20 (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

      Switch Condition

      Specified Condition

      H121-17 (IG1) - Body ground

      Ignition switch off

      0 to 1 V

      H121-19 (ACC) - Body ground

      Ignition switch off

      0 to 1 V

      H121-20 (IG2) - Body ground

      Ignition switch off

      0 to 1 V
    Table 1. Text in Illustration

    *a

    Front view of wire harness connector

    (to Engine Stop and Start ECU)

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  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

      Radio Receiver Assembly (for Radio Receiver Type)

      Tester Connection

      Condition

      Specified Condition

      H121-2 (BO1) - H1-4 (+B1)

      Always

      Below 1 Ω

      H121-3 (ACO) - H1-3 (ACC1)

      Always

      Below 1 Ω

      H121-2 (BO1) - Body ground

      Always

      10 kΩ or higher

      H121-3 (ACO) - Body ground

      Always

      10 kΩ or higher

      H1-4 (+B1) - Body ground

      Always

      10 kΩ or higher

      H1-3 (ACC1) - Body ground

      Always

      10 kΩ or higher

      Radio and Display Receiver Assembly (for Radio and Display Receiver Type)

      Tester Connection

      Condition

      Specified Condition

      H121-2 (BO1) - H107-4 (+B1)

      Always

      Below 1 Ω

      H121-3 (ACO) - H107-3 (ACC1)

      Always

      Below 1 Ω

      H121-2 (BO1) - Body ground

      Always

      10 kΩ or higher

      H121-3 (ACO) - Body ground

      Always

      10 kΩ or higher

      H107-4 (+B1) - Body ground

      Always

      10 kΩ or higher

      H107-3 (ACC1) - Body ground

      Always

      10 kΩ or higher

      Skid Control ECU (Brake Actuator Assembly)

      Tester Connection

      Condition

      Specified Condition

      H121-12 (IGO1) - A79-4 (IG1)

      Always

      Below 1 Ω

      H121-12 (IGO1) - Body ground

      Always

      10 kΩ or higher

      A79-4 (IG1) - Body ground

      Always

      10 kΩ or higher

      Steering Angle Sensor (Spiral with Sensor Cable Sub-assembly)

      Tester Connection

      Condition

      Specified Condition

      H121-12 (IGO1) - H128-5 (IG)

      Always

      Below 1 Ω

      H121-12 (IGO1) - Body ground

      Always

      10 kΩ or higher

      H128-5 (IG) - Body ground

      Always

      10 kΩ or higher

      Yaw Rate Sensor

      Tester Connection

      Condition

      Specified Condition

      H121-12 (IGO1) - H68-1 (IGA)

      Always

      Below 1 Ω

      H121-12 (IGO1) - Body ground

      Always

      10 kΩ or higher

      H68-1 (IGA) - Body ground

      Always

      10 kΩ or higher

      Power Steering ECU Assembly

      Tester Connection

      Condition

      Specified Condition

      H121-12 (IGO1) - H49-5 (IG)

      Always

      Below 1 Ω

      H121-12 (IGO1) - Body ground

      Always

      10 kΩ or higher

      H49-5 (IG) - Body ground

      Always

      10 kΩ or higher

      Combination Meter Assembly

      Tester Connection

      Condition

      Specified Condition

      H121-11 (IGO2) - H62-39 (IG+)

      Always

      Below 1 Ω

      H121-11 (IGO2) - Body ground

      Always

      10 kΩ or higher

      H62-39 (IG+) - Body ground

      Always

      10 kΩ or higher

      Instrument Panel Junction Block Assembly (Main Body ECU (Multiplex Network Body ECU))

      Tester Connection

      Condition

      Specified Condition

      H121-12 (IGO1) - DH-13 (IG)

      Always

      Below 1 Ω

      H121-12 (IGO1) - Body ground

      Always

      10 kΩ or higher

      DH-13 (IG) - Body ground

      Always

      10 kΩ or higher

      Inner Rear View Mirror Assembly (w/ Automatic Glare-resistant EC mirror)

      Tester Connection

      Condition

      Specified Condition

      H121-12 (IGO1) - Q9-4 (IG)

      Always

      Below 1 Ω

      H121-12 (IGO1) - Body ground

      Always

      10 kΩ or higher

      Q9-4 (IG) - Body ground

      Always

      10 kΩ or higher

      Tire Pressure Warning ECU and Receiver (w/ Tire Pressure Warning System)

      Tester Connection

      Condition

      Specified Condition

      H121-12 (IGO1) - N32-1 (IG)

      Always

      Below 1 Ω

      H121-12 (IGO1) - Body ground

      Always

      10 kΩ or higher

      N32-1 (IG) - Body ground

      Always

      10 kΩ or higher

      Back Sonar or Clearance Sonar Switch Assembly (w/ TOYOTA Parking Assist-sensor System)

      Tester Connection

      Condition

      Specified Condition

      H121-12 (IGO1) - H97-6 (IG)

      Always

      Below 1 Ω

      H121-12 (IGO1) - Body ground

      Always

      10 kΩ or higher

      H97-6 (IG) - Body ground

      Always

      10 kΩ or higher

    REPAIR OR REPLACE HARNESS OR CONNECTOR

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

    U122295E01
    Table 2. Text in Illustration

    *A

    for Radio Receiver Type

    *B

    for Radio and Display Receiver Type

    *C

    w/ Automatic Glare-resistant EC mirror

    *D

    w/ TOYOTA Parking Assist-sensor System

    *E

    w/ Tire Pressure Warning System

    -

    -

    *a

    Front view of wire harness connector

    (to Radio Receiver Assembly)

    *b

    Front view of wire harness connector

    (to Radio and Display Receiver Assembly)

    *c

    Front view of wire harness connector

    (to Skid Control ECU (Brake Actuator Assembly))

    *d

    Front view of wire harness connector

    (to Combination Meter Assembly)

    *e

    Front view of wire harness connector

    (to Steering Angle Sensor (Spiral with Sensor Cable Sub-assembly))

    *f

    Front view of wire harness connector

    (to Power Steering ECU Assembly)

    *g

    Front view of wire harness connector

    (to Instrument Panel Junction Block Assembly (Main Body ECU (Multiplex Network Body ECU)))

    *h

    Front view of wire harness connector

    (to Inner Rear View Mirror Assembly)

    *i

    Front view of wire harness connector

    (to Yaw Rate Sensor)

    *j

    Front view of wire harness connector

    (to Back Sonar or Clearance Sonar Switch Assembly)

    *k

    Front view of wire harness connector

    (to Tire Pressure Warning ECU and Receiver)

    -

    -

    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

      Radio Receiver Assembly (for Radio Receiver Type)

      Tester Connection

      Condition

      Specified Condition

      H1-4 (+B1) - Body ground

      Always

      9.5 to 14 V

      Radio and Display Receiver Assembly (for Radio and Display Receiver Type)

      Tester Connection

      Condition

      Specified Condition

      H107-4 (+B1) - 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

      Radio Receiver Assembly (for Radio Receiver Type)

      Tester Connection

      Switch Condition

      Specified Condition

      H1-3 (ACC1) - Body ground

      Ignition switch ACC

      9.5 to 14 V

      Radio and Display Receiver Assembly (for Radio and Display Receiver Type)

      Tester Connection

      Switch Condition

      Specified Condition

      H107-3 (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

      Switch Condition

      Specified Condition

      A79-4 (IG1) - Body ground

      Ignition switch ON

      9.5 to 14 V

      H62-39 (IG+) - Body ground

      Ignition switch ON

      9.5 to 14 V

      H128-5 (IG) - Body ground

      Ignition switch ON

      9.5 to 14 V

      H49-5 (IG) - Body ground

      Ignition switch ON

      9.5 to 14 V

      DH-13 (IG) - Body ground

      Ignition switch ON

      9.5 to 14 V

      H68-1 (IGA) - Body ground

      Ignition switch ON

      9.5 to 14 V

      Q9-4 (IG) - Body ground*1

      Ignition switch ON

      9.5 to 14 V

      H97-6 (IG) - Body ground*2

      Ignition switch ON

      9.5 to 14 V

      N32-1 (IG) - Body ground*3

      Ignition switch ON

      9.5 to 14 V

      • *1: w/ Automatic Glare-resistant EC Mirror

      • *2: w/ TOYOTA Parking Assist-sensor System

      • *3: w/ Tire Pressure Warning System

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

    REPLACE ENGINE STOP AND START ECU

    (Click here)

  5. CHECK AUDIO AND VISUAL SYSTEM OR NAVIGATION 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. for Radio Receiver Type/Radio and Display Receiver Type (Audio and Visual System):

      Check if the audio and visual system operates normally.

      OK

      Audio and visual system operates normally.

    5. for Radio and Display Receiver Type (Navigation system):

      Check if the navigation system operates normally.

      OK

      Navigation system operates normally.

    END

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

    1. Disconnect the H121 engine stop and start ECU connector.

    2. for Radio Receiver Type:

      Disconnect the H1 radio receiver assembly connector.

    3. for Radio and Display Receiver Type:

      Disconnect the H107 radio and display receiver assembly connector.

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

      Standard Resistance

      for Radio Receiver Type

      Tester Connection

      Condition

      Specified Condition

      H121-2 (BO1) - Body ground

      Always

      10 kΩ or higher

      H1-4 (+B1) - Body ground

      Always

      10 kΩ or higher

      H121-3 (ACO) - Body ground

      Always

      10 kΩ or higher

      H1-3 (ACC1) - Body ground

      Always

      10 kΩ or higher

      for Radio and Display Receiver Type

      Tester Connection

      Condition

      Specified Condition

      H121-2 (BO1) - Body ground

      Always

      10 kΩ or higher

      H107-4 (+B1) - Body ground

      Always

      10 kΩ or higher

      H121-3 (ACO) - Body ground

      Always

      10 kΩ or higher

      H107-3 (ACC1) - Body ground

      Always

      10 kΩ or higher
      Table 3. Result

      Result

      Proceed to

      OK (for Radio Receiver Type: Audio Visual System)

      A

      OK (for Radio and Display Receiver Type: Audio Visual System)

      B

      OK (for Radio and Display Receiver Type: Navigation System)

      C

      NG

      D

    GO TO AUDIO AND VISUAL SYSTEM

    (Click here)

    GO TO AUDIO AND VISUAL SYSTEM

    (Click here)

    GO TO NAVIGATION SYSTEM

    (Click here)

    REPAIR OR REPLACE HARNESS OR CONNECTOR