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 audio and visual 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* 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 signal.


    The backup boost converter supplies power to:

  • Main body ECU (multiplex network body ECU)

  • Inner rear view mirror

  • Dynamic radar cruise control system

  • Lane departure alert system

  • Road sign assist system

  • Forward recognition camera system

  • Tire pressure warning system

  • Audio and visual system

  • Blind spot monitor system

  • Simple Intelligent Parking Assist System*1

  • CAN communication system

  • Pre-collision system

  • Air conditioning system

  • Automatic high beam system


  • *1: w/ Simple Intelligent Parking Assist System

WIRING DIAGRAM


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 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 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

      B41 terminal:


      • Tire pressure warning system

      B42 terminal: All of the following will not operate


      • Audio and visual system

      IG41 terminal: All of the following will not operate


      • Inner rear view mirror assembly

      • Dynamic radar cruise control system

      • Lane departure alert system

      • Forward recognition camera system

      • Blind spot monitor system

      • Simple Intelligent Parking Assist System (w/ Simple Intelligent Parking Assist System)

      • CAN communication system

      • Pre-collision system

      • Air conditioning system

      • Automatic high beam 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 do not operate


      • Vehicle stability control system

      • Power steering system

      • Inner rear view mirror

      • Dynamic radar cruise control system

      • Lane departure alert system

      • Forward recognition camera system

      • Blind spot monitor system

      • Simple Intelligent Parking Assist System (w/ Simple Intelligent Parking Assist System)

      • CAN communication system

      • Pre-collision system

      • Air conditioning system

      • Automatic high beam 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: All of the following will not operate

      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 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)

      AC41 terminal:

      The audio and visual system will not function

      IG11 terminal:

      The audio and visual system will not function

      IG12 terminal:


      • The combination meter assembly will not function

      IG31 terminal:

      The Vehicle stability control system 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


      • Inner rear view mirror assembly

      • Vehicle stability control system

      • Power steering system

      • Dynamic radar cruise control system

      • Lane departure alert system

      • Forward recognition camera system

      • Blind spot monitor system

      • Simple Intelligent Parking Assist System (w/ Simple Intelligent Parking Assist System)

      • CAN communication system

      • Pre-collision system

      • Tire pressure warning system

      • Audio and visual system

      • Air conditioning system

      • Automatic high beam system

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

      • Open in BBC NO. 1 fuse circuit

      • Open in BBC NO. 2 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 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 AC41 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

      Tech Tips

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

      Converter circuit malfunction


      • Short between AC41 and +B

      • Short between IG12 and +B

      • Short between IG31 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

    A

    GO TO DIAGNOSTIC TROUBLE CODE CHART Click here

    C

    CHECK AUDIO AND VISUAL SYSTEM OR NAVIGATION SYSTEM Click here

    B

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


    1. A001XEIC36
      *a

      Front view of wire harness connector

      (to Engine Stop and Start ECU)

      Disconnect the 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
      A61-1 (BIN2) - Body ground Always 9.5 to 14 V
      A61-3 (BIN1) - Body ground Always 9.5 to 14 V

    3. Turn the ignition switch ACC.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      F77-19 (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
      F77-18 (IG2) - Body ground Ignition switch ON 9.5 to 14 V
      F77-21 (IG1) - 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
      F77-18 (IG2) - Body ground Ignition switch off 0 to 1 V
      F77-19 (ACC) - Body ground Ignition switch off 0 to 1 V
      F77-21 (IG1) - 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
      Radio and Display Receiver Assembly
      Tester Connection Condition Specified Condition
      F77-12 (B42) - F48-4 (+B1) Always Below 1 Ω
      F77-24 (AC41) - F48-3 (ACC1) Always Below 1 Ω
      F77-12 (B42) - Body ground and other terminals Always 10 kΩ or higher
      F77-24 (AC41) - Body ground and other terminals Always 10 kΩ or higher
      F48-4 (+B1) - Body ground and other terminals Always 10 kΩ or higher
      F48-3 (ACC1) - Body ground and other terminals Always 10 kΩ or higher
      Skid Control ECU (Brake Actuator Assembly)
      Tester Connection Condition Specified Condition
      F77-1 (IG31) - A42-36 (IG1) Always Below 1 Ω
      F77-1 (IG31) - Body ground and other terminals Always 10 kΩ or higher
      A42-36 (IG1) - Body ground and other terminals Always 10 kΩ or higher
      Spiral Cable with Sensor Sub-assembly
      Tester Connection Condition Specified Condition
      F77-1 (IG31) - F69-4 (IG1) Always Below 1 Ω
      F77-1 (IG31) - Body ground and other terminals Always 10 kΩ or higher
      F69-4 (IG1) - Body ground and other terminals Always 10 kΩ or higher
      Power Steering ECU Assembly
      Tester Connection Condition Specified Condition
      F77-6 (IG11) - F23-1 (IG) Always Below 1 Ω
      F77-6 (IG11) - Body ground and other terminals Always 10 kΩ or higher
      F23-1 (IG) - Body ground and other terminals Always 10 kΩ or higher
      Combination Meter Assembly
      Tester Connection Condition Specified Condition
      F77-10 (IG12) - F4-39 (IG+) Always Below 1 Ω
      F77-10 (IG12) - Body ground and other terminals Always 10 kΩ or higher
      F4-39 (IG+) - Body ground and other terminals Always 10 kΩ or higher
      Instrument Panel Junction Block Assembly (Main Body ECU (Multiplex Network Body ECU))
      Tester Connection Condition Specified Condition
      F77-3 (IG41) - 3A-15 Always Below 1 Ω
      F77-3 (IG41) - Body ground and other terminals Always 10 kΩ or higher
      3A-15 - Body ground and other terminals Always 10 kΩ or higher
      Pre-collision City Buzzer
      Tester Connection Condition Specified Condition
      F77-3 (IG41) - F54-2 (IG1) Always Below 1 Ω
      F77-3 (IG41) - Body ground and other terminals Always 10 kΩ or higher
      F54-2 (IG1) - Body ground and other terminals Always 10 kΩ or higher
      Forward Recognition Camera
      Tester Connection Condition Specified Condition
      F77-3 (IG41) - R5-7 (IGB) Always Below 1 Ω
      F77-3 (IG41) - Body ground and other terminals Always 10 kΩ or higher
      R5-7 (IGB) - Body ground and other terminals Always 10 kΩ or higher
      Forward Recognition Hood
      Tester Connection Condition Specified Condition
      F77-3 (IG41) - R8-1 (IG1) Always Below 1 Ω
      F77-3 (IG41) - Body ground and other terminals Always 10 kΩ or higher
      R8-1 (IG1) - Body ground and other terminals Always 10 kΩ or higher
      Blind Spot Monitor Sensor LH
      Tester Connection Condition Specified Condition
      F77-3 (IG41) - M62-5 (BLB) Always Below 1 Ω
      F77-3 (IG41) - Body ground and other terminals Always 10 kΩ or higher
      M62-5 (BLB) - Body ground and other terminals Always 10 kΩ or higher
      Blind Spot Monitor Sensor RH
      Tester Connection Condition Specified Condition
      F77-3 (IG41) - M63-5 (BRB) Always Below 1 Ω
      F77-3 (IG41) - Body ground and other terminals Always 10 kΩ or higher
      M63-5 (BRB) - Body ground and other terminals Always 10 kΩ or higher
      Inner Rear View Mirror Assembly
      Tester Connection Condition Specified Condition
      F77-3 (IG41) - R7-4 (IG) Always Below 1 Ω
      F77-3 (IG41) - Body ground and other terminals Always 10 kΩ or higher
      R7-4 (IG) - Body ground and other terminals Always 10 kΩ or higher
      Air Conditioning Control Assembly
      Tester Connection Condition Specified Condition
      F77-3 (IG41) - F61-10 (IG+) Always Below 1 Ω
      F77-3 (IG41) - Body ground and other terminals Always 10 kΩ or higher
      F61-10 (IG+) - Body ground and other terminals Always 10 kΩ or higher
      Clearance Warning ECU Assembly (w/ Simple Intelligent Parking Assist System)
      Tester Connection Condition Specified Condition
      F77-3 (IG41) - F38-8 (IG) Always Below 1 Ω
      F77-3 (IG41) - Body ground and other terminals Always 10 kΩ or higher
      F38-8 (IG) - Body ground and other terminals Always 10 kΩ or higher
      Millimeter Wave Radar Sensor Assembly
      Tester Connection Condition Specified Condition
      F77-3 (IG41) - A2-8 (IGB) Always Below 1 Ω
      F77-3 (IG41) - Body ground and other terminals Always 10 kΩ or higher
      A2-8 (IGB) - Body ground and other terminals Always 10 kΩ or higher
      Network Gateway ECU
      Tester Connection Condition Specified Condition
      F77-3 (IG41) - F74-11 (IG1) Always Below 1 Ω
      F77-3 (IG41) - Body ground and other terminals Always 10 kΩ or higher
      F74-11 (IG1) - Body ground and other terminals Always 10 kΩ or higher
      Door Control and Tire Pressure Monitoring System Receiver Assembly
      Tester Connection Condition Specified Condition
      F77-3 (IG41) - M23-1 (IG) Always Below 1 Ω
      F77-2 (B41) - M23-7 (+B) Always Below 1 Ω
      F77-3 (IG41) - Body ground and other terminals Always 10 kΩ or higher
      F77-2 (B41) - Body ground and other terminals Always 10 kΩ or higher
      M23-1 (IG) - Body ground and other terminals Always 10 kΩ or higher
      M23-7 (+B) - Body ground and other terminals 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.

      A001SKSC01
      *A w/ Simple Intelligent Parking Assist System - -
      *a

      Front view of wire harness connector

      (to Radio and Display Receiver Assembly)

      		 *b

      Front view of wire harness connector

      (to Forward Recognition Camera)
      *c

      Front view of wire harness connector

      (to Skid Control ECU (Brake Actuator Assembly))

      		 *d

      Front view of wire harness connector

      (to Inner Rear View Mirror 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 Forward Recognition Hood)

      		 *h

      Front view of wire harness connector

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

      Front view of wire harness connector

      (to Pre-collision City Buzzer)

      		 *j

      Front view of wire harness connector

      (to Door Control and Tire Pressure Monitoring System Receiver Assembly)
      *k

      Front view of wire harness connector

      (to Blind Spot Monitor Sensor LH)

      		 *l

      Front view of wire harness connector

      (to Blind Spot Monitor Sensor RH)
      *m

      Front view of wire harness connector

      (to Spiral Cable with Sensor Sub-assembly)

      		 *n

      Front view of wire harness connector

      (to Air Conditioning Control Assembly)
      *o

      Front view of wire harness connector

      (to Clearance Warning ECU Assembly)

      		 *p

      Front view of wire harness connector

      (to Millimeter Wave Radar Sensor Assembly)
      *q

      Front view of wire harness connector

      (to Network Gateway ECU)

      		 - -

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

      Tech Tips

      Measure the voltage at the corresponding terminals.

      Standard Voltage
      Radio and Display Receiver Assembly
      Tester Connection Condition Specified Condition
      F48-4 (+B1) - Body ground Always 10.5 to 16 V
      Door Control and Tire Pressure Monitoring System Receiver Assembly
      Tester Connection Condition Specified Condition
      M23-7 (+B) - 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.

      Tech Tips

      Measure the voltage at the corresponding terminals.

      Standard Voltage
      Radio and Display Receiver Assembly
      Tester Connection Switch Condition Specified Condition
      F48-3 (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.

      Tech Tips

      Measure the voltage at the corresponding terminals.

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A42-36 (IG1) - Body ground Ignition switch ON 10.5 to 16 V
      F69-4 (IG1) - Body ground Ignition switch ON 10.5 to 16 V
      F23-1 (IG) - Body ground Ignition switch ON 10.5 to 16 V
      F4-39 (IG+) - Body ground Ignition switch ON 10.5 to 16 V
      3A-15 - Body ground Ignition switch ON 10.5 to 16 V
      F54-2 (IG1) - Body ground Ignition switch ON 10.5 to 16 V
      R5-7 (IGB) - Body ground Ignition switch ON 10.5 to 16 V
      R8-1 (IG1) - Body ground Ignition switch ON 10.5 to 16 V
      M62-5 (BLB) - Body ground Ignition switch ON 10.5 to 16 V
      M63-5 (BRB) - Body ground Ignition switch ON 10.5 to 16 V
      R7-4 (IG) - Body ground Ignition switch ON 10.5 to 16 V
      F61-10 (IG+) - Body ground Ignition switch ON 10.5 to 16 V
      F38-8 (IG)*1 - Body ground Ignition switch ON 10.5 to 16 V
      A2-8 (IGB) - Body ground Ignition switch ON 10.5 to 16 V
      F74-11 (IG1) - Body ground Ignition switch ON 10.5 to 16 V
      M23-1 (IG) - Body ground Ignition switch ON 10.5 to 16 V
      M23-7 (+B) - Body ground Ignition switch ON 10.5 to 16 V

      • *1: w/ Simple Intelligent Parking Assist System

      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 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. Check if the audio and visual system operates normally.

      OK
      Audio and visual system operates normally.
      Result
      Proceed to
      NG
      OK

    OK

    END

    NG

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


    1. Disconnect the F77 engine stop and start ECU connector.

    2. Disconnect the F48 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
      F77-12 (B42) - Body ground and other terminals Always 10 kΩ or higher
      F77-24 (AC41) - Body ground and other terminals Always 10 kΩ or higher
      F48-4 (+B1) - Body ground and other terminals Always 10 kΩ or higher
      F48-3 (ACC1) - Body ground and other terminals Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    OK

    GO TO NAVIGATION SYSTEM Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR