STOP AND START SYSTEM > Backup Boost Converter Circuit


DESCRIPTION

The backup boost converter assembly supplements battery voltage to help prevent it from dropping when the engine is restarted during Stop and Start system control (Click here). This is done to prevent some electrical systems, such as the audio system, from being disabled due to low power supply voltage.
If any DTCs are output, troubleshoot for those DTCs first (Click here).

HINT:
  1. The backup boost converter assembly has a control circuit and internal relay for each electrical system it supplies, such as the meter, audio, and air conditioning systems. If a malfunction occurs in a circuit supplied by the backup boost converter, the relay opens and power supply to the applicable circuit will be shut off (remains open until the next trip).
    Turning the ignition switch off resets the internal relays. However, they will open again when the ignition switch is turned to ON if the malfunction in the circuit has not been repaired.
    The backup boost converter supplies power to the ABS/VSC, EPS, meter, audio, and air conditioning systems. If power is not supplied to any of these electrical systems, perform troubleshooting by referring to the table below.
  2. For more information on the effect of malfunction on Stop and Start system operation, refer to the System Description (Click here).


WIRING DIAGRAM

Refer to P323B (Click here).

INSPECTION PROCEDURE

NOTICE:
Inspect the fuses for circuits related to this system before performing the following inspection procedure.

1.CHECK PROBLEM SYMPTOM

  1. Determine the trouble area by referring to the table below.

    Effect on Vehicle
    		Trouble Area/Cause
    		Fail-safe
    		DTC Output
    		ECO Indicator Light
    		Proceed to
    		Symptom
    When the engine is restarted due to Stop and Start system control (Effect might not occur)
    1. The audio is reset
    2. The meter fades in and out
    3. EPS*1: While restarting, the steering feel is heavy
    4. Air conditioning system*1: None
    For *1, DTC might be stored
    		Converter internal malfunction
    1. Voltage of the control IC power source within the backup boost converter decreases
    2. Voltage of the control IC power source within the backup boost converter is too high
    3. Inappropriate DDON duty value is detected
    4. DDON duty cycle deviates beyond the allowable range
    		Stop and Start system control prohibited
    		P323B
    		Blinks
    		A
    		Backup boost converter output voltage cannot be increased when the engine is restarted due to Stop and Start system control
    External converter malfunction
    1. Open in DDON communication line
    2. Short in DDON communication line
    3. Short to GND in DDON communication line
    Battery voltage drop
    		Stop and Start system control prohibited
    		P323B
    		Blinks
    		A
    Depending on the type of relay that interrupts power supply
    BO1, ACO: The audio will not function
    IGO1: All of the following do not operate
    1. Skid control system (ABS/VSC)
    2. EPS (power steering)
    3. Air conditioning system
    IGO2: The combination meter will not function
    		A relay in the converter for one of the connected systems opens and the power supply is interrupted
    (occurs when overcurrent is detected for the respective system circuit)
    		Stop and Start System control might be prohibited (Depending on the type of component that interrupts the power supply from the backup boost converter, or depending on if DTC is stored by ECU.)
    		-
    		Not illuminated
    (May blink to indicate a malfunction in CAN communication)
    		B
    		Any system that the backup boost converter supplies with power is disabled due to its power supply being interrupted
    Depending on the type of the input wiring with malfunctions
    IG1: All of the following do not operate
    1. Skid control system (ABS/VSC)
    2. EPS (power steering system)
    3. Air conditioning system
    IG2: The meter will not function
    ACC: The audio will not function
    		Converter harness malfunction (converter input circuits)
    1. Open or short to GND in IG1 circuit
    2. Open or short to GND in IG2 circuit
    3. Open or short to GND in ACC circuit
    		Stop and Start system control prohibited
    		-
    		Not illuminated
    (May blink to indicate a malfunction in CAN communication)
    		B
    		Any system that the backup boost converter supplies with power is disabled due to its power supply being interrupted
    Depending on the relay system for the component where malfunction occurs
    Audio: The audio will not function
    Meter: The meter will not function
    ABS/VSC, EPS, A/C: Similar symptom will occur as when IGO1 is interrupted
    1. Skid control system (ABS/VSC)
    2. EPS (power steering system)
    3. Air conditioning system
    		Malfunction in circuit for the system that the converter supplies power
    (between converter and each system)
    1. Short to GND in combination meter circuit
    2. Short to GND in power steering ECU circuit
    3. Short to GND in A/C amplifier circuit
    4. Short to GND in skid control ECU circuit
    5. Short to GND in steering sensor circuit
    6. Short to GND in yaw rate and acceleration sensor circuit
    7. Short to GND in main body ECU circuit
    8. Short to GND in engine stop and start ECU circuit
    		Relay in the converter opens interrupting the power supply to the applicable system
    		-
    		Not illuminated
    (May blink to indicate a malfunction in CAN communication)
    		B
    		Any system that the backup boost converter supplies with power is disabled due to its power supply being interrupted
    All of the following will occur
    1. The audio will not function
    2. Skid control system (ABS/VSC)
    3. EPS (power steering system)
    4. Air conditioning system
    5. The combination meter will not function
    1. Open in converter fuse
    2. Short to GND in converter circuit
    3. Malfunction in backup boost converter
    4. Converter connector disconnected
    		Stop and Start system control prohibited
    		P323B
    		Not illuminated (meter system disabled)
    		A
    		All systems powered by the backup boost converter (refer to Wiring Diagram) do not operate
    Audio is interrupted
    (Stored for 1 trip)
    		Audio excessive volume
    "Overload" is shown in the Data List when the circuit is being protected. This status can be viewed by entering the following menus: Data List / State of BBC
    		Relay in the converter opens interrupting the power supply to the audio system
    (reset when the ignition switch is turned off)
    		-
    		Not illuminated
    		C
    		Audio system turns off while ignition switch ON and audio system cannot be turned on.
    (reset when the ignition switch is turned off)
    The condition differs depending on the circuit where the +B short occurs
    ACC+B short: The audio will not turn off
    IG1+B short: None
    IG2+B short: The meter will not turn off
    		Converter harness malfunction
    1. Short to +B in ACC circuit
    2. Short to +B in IG1 circuit
    3. Short to +B in IG2 circuit
    		-
    		-
    		Not illuminated
    		B
    		When the ignition switch is off, a system powered by the backup boost converter cannot be turned off



B
Go to step 2

C
Go to step 5
A

REPAIR OR REPLACE CIRCUITS INDICATED BY OUTPUT CODE (P323B) (Click here)  

2.INSPECT BACKUP BOOST CONVERTER (POWER SOURCE)


    A210722E02

  1. Disconnect the backup boost converter connector.

  1. Turn the ignition switch to ON.

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

    Standard Voltage:
    Tester Connection
    		Switch Condition
    		Specified Condition
    A54-3 (ACC) - Body ground
    		Ignition switch ON
    		10 to 14 V
    A54-13 (IG1) - Body ground
    		Ignition switch ON
    		10 to 14 V
    A54-15 (IG2) - Body ground
    		Ignition switch ON
    		10 to 14 V

  1. Turn the ignition switch off.

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

    Standard Voltage:
    Tester Connection
    		Switch Condition
    		Specified Condition
    A54-3 (ACC) - Body ground
    		Ignition switch off
    		0 to 1 V
    A54-13 (IG1) - Body ground
    		Ignition switch off
    		0 to 1 V
    A54-15 (IG2) - Body ground
    		Ignition switch off
    		0 to 1 V

    Text in Illustration 
    *1
    		Front view of wire harness connector:
    (to Backup Boost Converter)

  1. Reconnect the backup boost converter connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


3.CHECK HARNESS AND CONNECTOR (EACH SYSTEM - BACKUP BOOST CONVERTER)

  1. Disconnect the backup boost converter connector.

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

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

    Standard Resistance (for Audio System):
    Tester Connection
    		Switch Condition
    		Specified Condition
    A54-5 (BO1) - D61-4 (B)
    		Always
    		Below 1 Ω
    A54-12 (ACO) - D61-3 (ACC)
    		Always
    		Below 1 Ω
    A54-5 (BO1) or D61-4 (B) - Body ground
    		Always
    		10 kΩ or higher
    A54-12 (ACO) or D61-3 (ACC) - Body ground
    		Always
    		10 kΩ or higher

    Standard Resistance (for VSC/ABS System):
    Tester Connection
    		Switch Condition
    		Specified Condition
    for RHD:
    A54-14 (IGO1) - A17-34 (IG1)
    		Always
    		Below 1 Ω
    for LHD:
    A54-14 (IGO1) - A16-34 (IG1)
    		Always
    		Below 1 Ω
    for RHD:
    A54-14 (IGO1) or A17-34 (IG1) - Body ground
    		Always
    		10 kΩ or higher
    for LHD:
    A54-14 (IGO1) or A16-34 (IG1) - Body ground
    		Always
    		10 kΩ or higher

    Standard Resistance (for Steering Angle Sensor):
    Tester Connection
    		Switch Condition
    		Specified Condition
    A54-14 (IGO1) - D20-5 (IG)
    		Always
    		Below 1 Ω
    A54-14 (IGO1) or D20-5 (IG) - Body ground
    		Always
    		10 kΩ or higher

    Standard Resistance (for Power Steering System):
    Tester Connection
    		Switch Condition
    		Specified Condition
    A54-14 (IGO1) - D51-5 (IG)
    		Always
    		Below 1 Ω
    A54-14 (IGO1) or D51-5 (IG) - Body ground
    		Always
    		10 kΩ or higher

    Standard Resistance (for Yaw Rate and Acceleration Sensor):
    Tester Connection
    		Switch Condition
    		Specified Condition
    A54-14 (IGO1) - D58-4 (IG)
    		Always
    		Below 1 Ω
    A54-14 (IGO1) or D58-4 (IG) - Body ground
    		Always
    		10 kΩ or higher

    Standard Resistance (for Air Conditioning System):
    Tester Connection
    		Switch Condition
    		Specified Condition
    A54-14 (IGO1) - D15-1 (IG+)
    		Always
    		Below 1 Ω
    A54-14 (IGO1) or D15-1 (IG+) - Body ground
    		Always
    		10 kΩ or higher

    Standard Resistance (for Meter/Gauge System):
    Tester Connection
    		Switch Condition
    		Specified Condition
    A54-16 (IGO2) - D1-1 (IG+)
    		Always
    		Below 1 Ω
    A54-16 (IGO2) or D1-1 (IG+) - Body ground
    		Always
    		10 kΩ or higher

  1. Reconnect the backup boost converter connector.

  1. Reconnect the connector to the corresponding system ECU/sensor.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR (CORRESPONDING SYSTEM - BACKUP BOOST CONVERTER)
OK


4.INSPECT BACKUP BOOST CONVERTER (OUTPUT VOLTAGE FOR EACH SYSTEM)


    A217718E01

  1. Turn the ignition switch off.

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

  1. Turn the ignition switch to ON.

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

    HINT:
    Measure the voltage at the corresponding terminals.

    Standard Voltage:
    Tester Connection
    		Switch Condition
    		Specified Condition
    for RHD:
    A17-34 (IG1) - Body ground
    		Ignition switch ON
    		10 to 14 V
    for LHD:
    A16-34 (IG1) - Body ground
    		Ignition switch ON
    		10 to 14 V
    D61-4 (B) - Body ground
    		Always
    		10 to 14 V
    D61-3 (ACC) - Body ground
    		Ignition switch ON
    		10 to 14 V
    D1-1 (IG+) - Body ground
    		Ignition switch ON
    		10 to 14 V
    D20-5 (IG) - Body ground
    		Ignition switch ON
    		10 to 14 V
    D51-5 (IG) - Body ground
    		Ignition switch ON
    		10 to 14 V
    D58-4 (IG) - Body ground
    		Ignition switch ON
    		10 to 14 V
    D15-1 (IG+) - Body ground
    		Ignition switch ON
    		10 to 14 V

    Text in Illustration 
    *A
    		for RHD:
    *B
    		for LHD:
    *1
    		Front view of wire harness connector:
    (to Brake Actuator Assembly (Skid Control ECU))
    *2
    		Front view of wire harness connector:
    (to Brake Actuator Assembly (Skid Control ECU))
    *3
    		Front view of wire harness connector:
    (to Radio Receiver Assembly)
    *4
    		Front view of wire harness connector:
    (to Combination Meter Assembly)
    *5
    		Front view of wire harness connector:
    (to Steering Angle Sensor)
    *6
    		Front view of wire harness connector:
    (to Power Steering ECU)
    *7
    		Front view of wire harness connector:
    (to Yaw Rate and Acceleration Sensor)
    *8
    		Front view of wire harness connector:
    (to Air Conditioning Amplifier)

  1. Reconnect the connector to the corresponding system ECU/sensor.



NG
REPLACE BACKUP BOOST CONVERTER (Click here)
OK

INSPECT POWER SOURCE CIRCUIT OF CORRESPONDING SYSTEM 

5.INSPECT AUDIO SYSTEM OPERATION

  1. Turn the ignition switch off and wait for 1 minute.

  1. Lower the audio volume.

  1. Turn the ignition switch to ON.

  1. Check if the audio system operates normally.

    OK:
    Audio system operates normally.



NG
Go to step 6
OK

END (VOLUME WAS TOO HIGH) 

6.CHECK HARNESS AND CONNECTOR (BACKUP BOOST CONVERTER - AUDIO SYSTEM)

  1. Disconnect the backup boost converter connector.

  1. Disconnect the audio system connector.

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

    Standard Resistance (Check for Short):
    Tester Connection
    		Condition
    		Specified Condition
    A54-5 (BO1) or D61-4 (B) - body ground
    		Always
    		10 kΩ or higher
    A54-12 (ACO) or D61-3 (ACC) - body ground
    		Always
    		10 kΩ or higher

  1. Reconnect the backup boost converter connector.

  1. Reconnect the audio system connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

CHECK AUDIO SYSTEM (POWER SOURCE CIRCUIT)