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*1 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).

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

The backup boost converter supplies power to:


  • Navigation system

  • Rear seat entertainment system

  • Power steering system

  • Electric parking brake system

  • Meter / Gauge system

  • Vehicle stability control system

  • TOYOTA parking assist-sensor system

  • Air conditioning system

The eco run vehicle converter assembly (external backup boost converter) supplies power to:


  • Navigation system

WIRING DIAGRAM

A01UD6UE01
A01UCMJE05
A01UEXLE02
A01UFHVE02

CAUTION / NOTICE / HINT

Note


  • When replacing the engine stop and start ECU with a new one, make sure to download the previous status (number of starter operations) of the old engine stop and start ECU. After replacing the engine stop and start ECU, turn the engine switch on (IG) and wait 20 seconds, then confirm that "OK" is displayed for the Data List item "Oper Prohibition (O/P Air Bleeding)". Then upload the previous status (number of starter operations) to the 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 ECU 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,


      • Audio and visual 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

      • CPU duty malfunction

      • Communication cycle error

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

      Systems on the converter output side do not operate

      B42 terminal: All of the following will not operate,


      • TOYOTA parking assist-sensor system

      B43 terminal: All of the following will not operate,


      • Air conditioning system

      • Navigation system

      • Rear seat entertainment system

      IG41 terminal: All of the following will not operate,


      • TOYOTA parking assist-sensor system

      • Air conditioning 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 will not operate,


      • Power steering system

      • Vehicle stability control system

      • TOYOTA parking assist-sensor system

      • Air conditioning system

      IG2 terminal: The meter / gauge system will not function

      ACC terminal: All of the following will not operate,


      • Air conditioning system

      • Navigation system

      • Rear seat entertainment 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 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)

      A41 terminal:


      • The air conditioning system will not operate.

      • The navigation system will not operate.

      • The rear seat entertainment system will not operate.

      IG11 terminal: The power steering system will not operate

      IG12 terminal: The meter / gauge system will not operate

      IG31 terminal: The vehicle stability control system will not operate

      B11 terminal: The electric parking brake system will not operate

      IL41 terminal: The air conditioning system 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


      • Navigation system

      • Rear seat entertainment system

      • Power steering system

      • Electric parking brake system

      • Meter / Gauge system

      • Vehicle stability control system

      • TOYOTA parking assist-sensor system

      • Air conditioning 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 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 navigation system (audio system) (Returns to normal when the engine switch is turned off) - Does not blink

      If overcurrent is detected in the navigation system, system operation is disabled while the engine switch is on (IG)

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

      		 C

      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 IGO2 and +B

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

      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

      • Engine switch does not turn on (ACC)

      • Engine switch does not turn off

      		 B
      Result
      Proceed to
      A
      B
      C

    A

    GO TO DTC CHART Click here

    C

    CHECK AUDIO AND VISUAL SYSTEM Click here

    B

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


    1. A01UEH1C05
      *a

      Front view of wire harness connector

      (to Engine Stop and Start ECU)

      Disconnect the A59 and G50 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
      A59-1 (BIN2) - Body ground Always 9.5 to 14 V
      A59-3 (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 Condition Specified Condition
      G50-19 (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 Condition Specified Condition
      G50-18 (IG2) - Body ground Engine switch on (IG) 9.5 to 14 V
      G50-21 (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 Condition Specified Condition
      G50-20 (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 Condition Specified Condition
      G50-18 (IG2) - Body ground Engine switch off 0 to 1 V
      G50-19 (ACC) - Body ground Engine switch off 0 to 1 V
      G50-21 (IG1) - Body ground Engine 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
      Parking Brake ECU Assembly
      Tester Connection Condition Specified Condition
      G50-23 (B11) - K14-3 (BECU) Always Below 1 Ω
      G50-23 (B11) - Body ground Always 10 kΩ or higher
      K14-3 (BECU) - Body ground Always 10 kΩ or higher
      Navigation Receiver Assembly
      Tester Connection Condition Specified Condition
      G50-12 (B42) - F1-4 (+B1) Always Below 1 Ω
      G50-24 (AC41) - F1-3 (ACC1) Always Below 1 Ω
      G50-12 (B42) - Body ground Always 10 kΩ or higher
      F1-4 (+B1) - Body ground Always 10 kΩ or higher
      G50-24 (AC41) - Body ground Always 10 kΩ or higher
      F1-3 (ACC1) - Body ground Always 10 kΩ or higher
      Television Display Assembly
      Tester Connection Condition Specified Condition
      G50-12 (B42) - S36-1 (+B) Always Below 1 Ω
      G50-24 (AC41) - S36-2 (ACC) Always Below 1 Ω
      G50-12 (B42) - Body ground Always 10 kΩ or higher
      S36-1 (+B) - Body ground Always 10 kΩ or higher
      G50-24 (AC41) - Body ground Always 10 kΩ or higher
      S36-2 (ACC) - Body ground Always 10 kΩ or higher
      Air Conditioning Control Assembly
      Tester Connection Condition Specified Condition
      G50-3 (IG41) - G30-5 (IG+) Always Below 1 Ω
      G50-11 (B43) - G30-1 (+B) Always Below 1 Ω
      G50-24 (AC41) - G30-6 (ACC) Always Below 1 Ω
      G50-25 (IL41) - G30-2 (ILL+) Always Below 1 Ω
      G50-3 (IG41) - Body ground Always 10 kΩ or higher
      G30-5 (IG+) - Body ground Always 10 kΩ or higher
      G50-11 (B43) - Body ground Always 10 kΩ or higher
      G30-1 (+B) - Body ground Always 10 kΩ or higher
      G50-24 (AC41) - Body ground Always 10 kΩ or higher
      G30-6 (ACC) - Body ground Always 10 kΩ or higher
      G50-25 (IL41) - Body ground Always 10 kΩ or higher
      G30-2 (ILL+) - Body ground Always 10 kΩ or higher
      Power Steering ECU Assembly
      Tester Connection Condition Specified Condition
      G50-6 (IG11) - G20-1 (IG) Always Below 1 Ω
      G50-6 (IG11) - Body ground Always 10 kΩ or higher
      G20-1 (IG) - Body ground Always 10 kΩ or higher
      Combination Meter Assembly
      Tester Connection Condition Specified Condition
      G50-10 (IG12) - G16-2 (IG+) Always Below 1 Ω
      G50-10 (IG12) - Body ground Always 10 kΩ or higher
      G16-2 (IG+) - Body ground Always 10 kΩ or higher
      Skid Control ECU (Brake Actuator Assembly)
      Tester Connection Condition Specified Condition
      G50-1 (IG31) - A50-12 (IG1) Always Below 1 Ω
      G50-1 (IG31) - Body ground Always 10 kΩ or higher
      A50-12 (IG1) - Body ground Always 10 kΩ or higher
      Spiral with Sensor Cable Sub-assembly
      Tester Connection Condition Specified Condition
      G50-1 (IG31) - G12-4 (IG) Always Below 1 Ω
      G50-1 (IG31) - Body ground Always 10 kΩ or higher
      G12-4 (IG) - Body ground Always 10 kΩ or higher
      Clearance Warning ECU Assembly
      Tester Connection Condition Specified Condition
      G50-3 (IG41) - G59-1 (IG) Always Below 1 Ω
      G50-3 (IG41) - Body ground Always 10 kΩ or higher
      G59-1 (IG) - Body ground Always 10 kΩ or higher
      Integratin Control and Panel Assembly
      Tester Connection Condition Specified Condition
      G50-3 (IG41) - S8-7 (IG) Always Below 1 Ω
      G50-25 (IL41) - S8-1 (ILL+) Always Below 1 Ω
      G50-3 (IG41) - Body ground Always 10 kΩ or higher
      S8-7 (IG) - Body ground Always 10 kΩ or higher
      G50-25 (IL41) - Body ground Always 10 kΩ or higher
      S8-1 (ILL+) - 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.

      A01UDBCC01
      *A w/ Navigation System *B w/ Rear Seat Entertainment System
      *a

      Front view of wire harness connector

      (to Parking Brake ECU Assembly)

      		 *b

      Front view of wire harness connector

      (to Navigation Receiver Assembly)
      *c

      Front view of wire harness connector

      (to Television Display Assembly)

      		 *d

      Front view of wire harness connector

      (to Air Conditioning Control Assembly)
      *e

      Front view of wire harness connector

      (to Power Steering ECU Assembly)

      		 *f

      Front view of wire harness connector

      (to Combination Meter Assembly)
      *g

      Front view of wire harness connector

      (to Skid Control ECU (Brake Actuator Assembly))

      		 *h

      Front view of wire harness connector

      (to Spiral with Sensor Cable Sub-assembly)
      *i

      Front view of wire harness connector

      (to Clearance Warning ECU Assembly)

      		 *j

      Front view of wire harness connector

      (to Integration Control and Panel Assembly)

    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
      K14-3 (BECU) - Body ground Always 10.5 to 16 V
      F1-4 (+B1) - Body ground Always 10.5 to 16 V
      S36-1 (+B) - Body ground Always 10.5 to 16 V
      G30-1 (+B) - Body ground Always 10.5 to 16 V

    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
      F1-3 (ACC1) - Body ground Engine switch on (ACC) 10.5 to 16 V
      S36-2 (ACC) - Body ground Engine switch on (ACC) 10.5 to 16 V
      G30-6 (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
      G20-1 (IG) - Body ground Engine switch on (IG) 10.5 to 16 V
      G16-2 (IG+) - Body ground Engine switch on (IG) 10.5 to 16 V
      A50-12 (IG1) - Body ground Engine switch on (IG) 10.5 to 16 V
      G12-4 (IG) - Body ground Engine switch on (IG) 10.5 to 16 V
      G59-1 (IG) - Body ground Engine switch on (IG) 10.5 to 16 V
      G30-5 (IG+) - Body ground Engine switch on (IG) 10.5 to 16 V
      S8-7 (IG) - Body ground Engine switch on (IG) 10.5 to 16 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.

      Tech Tips

      Measure the voltage at the corresponding terminals.

      Standard Voltage
      Tester Connection Condition Specified Condition
      G30-2 (ILL+) - Body ground Headlight dimmer switch (light control switch) in tail or head position 10.5 to 16 V
      S8-1 (ILL+) - Body ground Headlight dimmer switch (light control switch) in tail or head position 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 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.

    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
      OK
      NG

    OK

    END

    NG

  6. CHECK HARNESS AND CONNECTOR (ECO RUN VEHICLE CONVERTER ASSEMBLY (EXTERNAL BACKUP BOOST CONVERTER) ACO, BO1, BO2 TERMINAL CIRCUIT)


    1. Disconnect the A20 eco run vehicle converter assembly (external backup boost converter) connector.

    2. Disconnect the F9 stereo component amplifier assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A20-5 (BO1) - Body ground Always 10 kΩ or higher
      F6-1 (+B) - Body ground Always 10 kΩ or higher
      F6-16 (+B2) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    OK

    GO TO AUDIO AND VISUAL SYSTEM Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR