STOP AND START SYSTEM, Diagnostic DTC:P323A19

DTC Code DTC Name
P323A19 Backup Boost Converter "A" Circuit Current Above Threshold

DESCRIPTION

A backup boost converter is built into the engine stop and start ECU.

The backup boost converter helps maintain battery voltage to prevent various functions from failing if power source voltage supplied from the backup boost converter drops due to the high electrical load when the engine is restarted by stop and start control.

The backup boost converter helps maintain the power source voltage if the battery voltage drops due to the high electrical load when the engine is restarted by stop and start control.

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 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 turned on (IG).

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


    The backup boost converter supplies power to:

  • Vehicle stability control system

  • Power steering system

  • Dynamic radar cruise control system

  • Inner rear view mirror assembly (w/ EC Mirror)

  • Lane departure alert system

  • Air conditioning system

  • CAN communication system (Network gateway ECU)

  • Panoramic view monitor system

  • Blind spot monitor system

  • Meter / Gauge system (Headup display)

  • Remote operation controller assembly

  • Telematics System

  • Tire pressure warning system

  • Entry and start system (w/ Entry and Start System)

  • Push-button start (w/o Entry and Start System)

  • Lexus Parking Assist-sensor System

DTC No. Detection Item DTC Detection Condition Trouble Area Warning Indicate Memory Note
P323A19 Backup Boost Converter "A" Circuit Current Above Threshold

The following condition continues for 1 second or more (1 trip detection logic):


  • Overcurrent is detected at the B41, B42, B43, IG41 and EMOP terminals in the engine stop and start ECU

  • Engine stop and start ECU

  • Wire harness or connector

  • Tire pressure warning ECU and receiver (Door control and tire pressure monitoring system receiver assembly) (Tire Pressure Warning ECU and Receiver (for RH Side))

  • Tire pressure warning ECU and receiver (Tire Pressure Warning ECU and Receiver (for LH Side))

  • Blind spot monitor sensor LH (w/ Blind Spot Monitor System)

  • Blind spot monitor sensor RH (w/ Blind Spot Monitor System)

  • Clearance waring ECU assembly (w/ Lexus Parking Assist-sensor System)

  • Millimeter wave radar sensor assembly (w/ Dynamic Radar Cruise Control System)

  • Driving support ECU assembly (w/ Dynamic Radar Cruise Control System)

  • Network gateway ECU

  • Forward recognition camera (w/ Lane Departure Alert System)

  • Inner rear view mirror assembly (w/ EC Mirror)

  • Combination meter mirror ECU (w/ Headup Display)

  • Air conditioning control assembly

  • Remote operation controller assembly

  • Navigation ECU

  • Radio receiver assembly

  • Multi-display assembly

 Blinks DTC stored SAE Code: P323A

CONFIRMATION DRIVING PATTERN


  1. CONFIRMATION AFTER TROUBLESHOOTING

    Tech Tips


    • If the cable is disconnected from the battery terminal, stop and start control is prohibited until refresh charge is completed.

      In this case, let the vehicle idle to complete the refresh charge. The refresh charge is complete when the Data List item Status of Battery Charge Control changes from "Refresh Charge Mode". (Usually, idling the engine for 5 to 60 minutes with the battery fluid temperature at 11°C (52°F) or higher, the refresh charge will be completed.)

    • If the GTS is not available and the Data List item Status of Battery Charge Control cannot be checked, charge the battery by idling the engine for approximately 5 to 60 minutes or driving the vehicle, and then drive the vehicle and check that stop and start control operates.

      If the engine is started with the hood open, the system determines that a jump start has occurred. Therefore, make sure that the hood is closed before starting the engine and driving the vehicle.

    • After the refresh charge completes, turn the engine switch off, wait for at least 30 seconds, and then start the engine again. If the vehicle enters refresh charge mode again while the engine is idling, the initial refresh charge did not properly complete, so wait for the refresh charge to complete.

    • Allow the engine to idle for 3 minutes after it is warmed up and check that the engine idle speed is within 50 rpm of the target idle speed.


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Clear the DTCs.


      Powertrain > Stop and Start > Clear DTCs

    5. Start the engine and warm it up.

    6. Drive the vehicle at 7 km/h (4.3 mph) or more.

      CAUTION:

      When performing Confirmation Driving Pattern, obey all speed limits and traffic laws.

    7. Depress the brake pedal and stop the vehicle.

    8. Keep the engine stopped by stop and start control for 1 second or more. (Keep the shift lever in D.)

    9. Release the brake pedal with the shift lever in D to start the engine.

      Tech Tips

      If the engine cranks slowly when the engine is restarted, it can be determined that the battery voltage is low.

    10. Check that DTCs are not output.


      Powertrain > Stop and Start > Trouble Codes

  2. STOP AND START SYSTEM OPERATION CHECK

    Tech Tips


    • If the cable is disconnected from the battery terminal, stop and start control is prohibited until refresh charge is completed.

      In this case, let the vehicle idle to complete the refresh charge. The refresh charge is complete when the Data List item Status of Battery Charge Control changes from "Refresh Charge Mode". (Usually, idling the engine for 5 to 60 minutes with the battery fluid temperature at 11°C (52°F) or higher, the refresh charge will be completed.)

    • If the GTS is not available and the Data List item Status of Battery Charge Control cannot be checked, charge the battery by idling the engine for approximately 5 to 60 minutes or driving the vehicle, and then drive the vehicle and check that stop and start control operates.

      If the engine is started with the hood open, the system determines that a jump start has occurred. Therefore, make sure that the hood is closed before starting the engine and driving the vehicle.

    • After the refresh charge completes, turn the engine switch off, wait for at least 30 seconds, and then start the engine again. If the vehicle enters refresh charge mode again while the engine is idling, the initial refresh charge did not properly complete, so wait for the refresh charge to complete.


    1. Start the engine and warm it up.

    2. Turn the air conditioning system off.

    3. Drive the vehicle at 7 km/h (4.3 mph) or more.

      CAUTION:

      When performing Confirmation Driving Pattern, obey all speed limits and traffic laws.

    4. Depress the brake pedal and stop the vehicle.

    5. Allow the engine to stop by stop and start control. (Keep the shift lever in D.)

    6. Release the brake pedal with the shift lever in D to start the engine.

WIRING DIAGRAM

B0059YYE03
B005B7EE01
B005AIJE01
B00575BE02
B0057U2E01

CAUTION / NOTICE / HINT

Note


  • for 8AR-FTS:

    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

  • for 3ZR-FAE:

    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 "Stop&Start Operating Permission (Discharged Oil Pump Air)". 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 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.

Tech Tips


  • If electrical load from additional devices installed to the vehicle (aftermarket audio system, etc.) is applied to the B41, B42, B43 or IG41 terminal in the engine stop and start ECU, the fuse function of the backup boost converter may operate.

    If the fuse function of the backup boost converter operates, any systems connected to the B41, B42, B43 or IG41 terminal in the engine stop and start ECU will not operate.

  • DTCs for the stop and start system are not cleared even if the malfunction has been repaired. After repairing the malfunction, be sure to clear the DTCs.

    Click here

  • Using the GTS, read the freeze frame data before troubleshooting. System condition information is recorded as freeze frame data the moment a DTC is stored. This information can be useful when troubleshooting.

    Click here

PROCEDURE


  1. CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - BBC NO. 1 FUSE AND BBC NO. 3 FUSE)


    1. Disconnect the engine stop and start ECU connector.

    2. Remove the BBC NO. 1 fuse and BBC NO. 3 fuse from the No. 1 engine room relay block and junction block.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A73-1 (BIN2) - BBC NO. 3 fuse terminal 2 Always Below 1 Ω
      A73-3 (BIN1) - BBC NO. 1 fuse terminal 2 Always Below 1 Ω
      A73-1 (BIN2) or BBC NO. 3 fuse terminal 2 - Body ground and other terminals Always 10 kΩ or higher
      A73-3 (BIN1) or BBC NO. 1 fuse terminal 2 - Body ground and other terminals Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  2. CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - EACH ECU OR SENSOR)


    1. Disconnect the engine stop and start ECU connector.

    2. Disconnect the P11 tire pressure warning ECU and receiver (door control and tire pressure monitoring system receiver assembly) connector. (Tire Pressure Warning ECU and Receiver (for RH Side))

    3. Disconnect the Q46 tire pressure warning ECU and receiver connector. (Tire Pressure Warning ECU and Receiver (for LH Side))

    4. Disconnect the V1 blind spot monitor sensor LH connector. (w/ Blind Spot Monitor System)

    5. Disconnect the X1 blind spot monitor sensor RH connector. (w/ Blind Spot Monitor System)

    6. Disconnect the I20 clearance waring ECU assembly connector. (w/ Lexus Parking Assist-sensor System)

    7. Disconnect the B13 millimeter wave radar sensor assembly connector. (w/ Dynamic Radar Cruise Control System)

    8. Disconnect the I159 driving support ECU assembly connector. (w/ Dynamic Radar Cruise Control System)

    9. Disconnect the I164 network gateway ECU connector.

    10. Disconnect the T17 forward recognition camera connector. (w/ Lane Departure Alert System)

    11. Disconnect the T5 inner rear view mirror connector. (w/ EC Mirror)

    12. Disconnect the J5 combination meter mirror ECU connector. (w/ Headup Display)

    13. Disconnect the I13 air conditioning control assembly connector.

    14. Disconnect the I71 remote operation controller assembly connector. (w/ Navigation System)

    15. Disconnect the I160 navigation ECU connector. (w/ Navigation System)

    16. Disconnect the I152 radio receiver assembly connector.

    17. Disconnect the I42 multi-display assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      I57-3 (IG41) - P11-1 (IG)*1 Always Below 1 Ω
      I57-3 (IG41) - Q46-1 (IG)*2 Always Below 1 Ω
      I57-3 (IG41) - V1-5 (BLB)*3 Always Below 1 Ω
      I57-3 (IG41) - X1-5 (BRB)*3 Always Below 1 Ω
      I57-3 (IG41) - I20-1 (IG)*4 Always Below 1 Ω
      I57-3 (IG41) - B13-8 (IGB)*5 Always Below 1 Ω
      I57-3 (IG41) - I159-7 (B)*5 Always Below 1 Ω
      I57-3 (IG41) - I164-11 (IG1) Always Below 1 Ω
      I57-3 (IG41) - T17-7 (IGB)*6 Always Below 1 Ω
      I57-3 (IG41) - T5-1 (IG)*7 Always Below 1 Ω
      I57-3 (IG41) - J5-1 (IG)*8 Always Below 1 Ω
      I57-3 (IG41) - I13-8 (IG+) Always Below 1 Ω
      I57-2 (B41) - I71-1 (+B)*9 Always Below 1 Ω
      I57-2 (B41) -I160-10 (+B)*9 Always Below 1 Ω
      I57-2 (B41) - P11-7 (+B)*1 Always Below 1 Ω
      I57-12 (B42) - I152-4 (+B1) Always Below 1 Ω
      I57-11 (B43) - I42-12 (B) Always Below 1 Ω
      I57-3 (IG41) or P11-1 (IG)*1 - Body ground and other terminals Always 10 kΩ or higher
      I57-3 (IG41) or Q46-1 (IG)*2 - Body ground and other terminals Always 10 kΩ or higher
      I57-3 (IG41) or V1-5 (BLB)*3 - Body ground and other terminals Always 10 kΩ or higher
      I57-3 (IG41) or X1-5 (BRB)*3 - Body ground and other terminals Always 10 kΩ or higher
      I57-3 (IG41) or I20-1 (IG)*4 - Body ground and other terminals Always 10 kΩ or higher
      I57-3 (IG41) or B13-8 (IGB)*5 - Body ground and other terminals Always 10 kΩ or higher
      I57-3 (IG41) or I159-7 (B)*5 - Body ground and other terminals Always 10 kΩ or higher
      I57-3 (IG41) or I164-11 (IG1) - Body ground and other terminals Always 10 kΩ or higher
      I57-3 (IG41) or T17-7 (IGB)*6 - Body ground and other terminals Always 10 kΩ or higher
      I57-3 (IG41) or T5-1 (IG)*7 - Body ground and other terminals Always 10 kΩ or higher
      I57-3 (IG41) or J5-1 (IG)*8 - Body ground and other terminals Always 10 kΩ or higher
      I57-3 (IG41) or I13-8 (IG+) - Body ground and other terminals Always 10 kΩ or higher
      I57-2 (B41) or I71-1 (+B)*9 - Body ground and other terminals Always 10 kΩ or higher
      I57-2 (B41) or I160-10 (+B)*9 - Body ground and other terminals Always 10 kΩ or higher
      I57-2 (B41) or P11-7 (+B)*1 - Body ground and other terminals Always 10 kΩ or higher
      I57-12 (B42) or I152-4 (+B1) - Body ground and other terminals Always 10 kΩ or higher
      I57-11 (B43) or I42-12 (B) - Body ground and other terminals Always 10 kΩ or higher

      • *1: Tire Pressure Warning ECU and Receiver (for RH Side)

      • *2: Tire Pressure Warning ECU and Receiver (for RH Side)

      • *3: w/ Blind Spot Monitor System

      • *4: w/ Lexus Parking Assist-sensor System

      • *5: w/ Dynamic Radar Cruise Control System

      • *6: w/ Lane Departure Alert System

      • *7: w/ EC Mirror

      • *8: w/ Headup Display

      • *9: w/ Navigation System

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. CHECK ENGINE STOP AND START ECU

    B00593SC08
    *a

    Component without harness connected

    (Engine Stop and Start ECU)

    		 - -

    1. Disconnect the engine stop and start ECU connectors.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      I57-2 (B41) - A38-6 (DGND) Always 10 kΩ or higher
      I57-3 (IG41) - A38-6 (DGND) Always 10 kΩ or higher
      I57-11 (B43) - A38-6 (DGND) Always 10 kΩ or higher
      I57-12 (B42) - A38-6 (DGND) Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE ENGINE STOP AND START ECU Click here

    OK

  4. CHECK VEHICLE CONDITION (B41, B42, B43 OR IG41 CIRCUIT)


    1. Check that additional devices installed to the vehicle (aftermarket audio system, etc.) are not connected to the B41, B42, B43 or IG41 terminal circuit of the engine stop and start ECU.

      Result
      Result Proceed to
      Load from an additional device installed to the vehicle (aftermarket audio system, etc.) is not applied. A
      Load from an additional device installed to the vehicle (aftermarket audio system, etc.) is applied. B

    A

    TROUBLESHOOT ECUS CONNECTED TO TERMINALS B41, B42, B43 AND IG41

    B

    END (REMOVE ADDITIONAL DEVICE)