STOP AND START SYSTEM, Diagnostic DTC:P1540

DTC Code DTC Name
P1540 Brake Booster Sensor Circuit (Open or Short)

DESCRIPTION

The engine stop and start ECU determines changes in the brake booster assembly pressure based on the voltage signal received from the vacuum sensor assembly in the brake booster assembly.

If the engine stop and start ECU judges that the signal received from the vacuum sensor assembly is abnormal, it stores DTC P1540 and blinks the stop and start cancel indicator light.

A01M12OE02
DTC No. Detection Item DTC Detection Condition Trouble Area Warning Indicate Memory
P1540 Brake Booster Sensor Circuit (Open or Short)

Both of the following conditions are met for 2 seconds or more (1 trip detection logic):


  • Open or short in vacuum sensor assembly circuit

  • Ignition switch is turned to ON

  • Vacuum sensor assembly

  • Engine stop and start ECU

  • Wire harness or connector

 Blinks DTC stored

CONFIRMATION DRIVING PATTERN

Tech Tips

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

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  1. CONFIRMATION AFTER TROUBLESHOOTING

    Tech Tips


    • If the cable is disconnected from the negative (-) battery terminal, stop and start control is prohibited until refresh charge is completed. In this case, drive the vehicle approximately 5 to 40 minutes until refresh charge is completed and stop and start control operation is permitted.

    • 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 ignition switch to ON and turn the GTS on.

    3. Clear the DTCs.

      Click here


      Powertrain > Stop and Start > Clear DTCs

    4. Start the engine and allow it to idle for 15 seconds or more.

    5. Stop the engine and turn the ignition switch to ON.

    6. Turn the GTS on.

    7. Enter the following menus: Powertrain / Stop and Start / Data List / Brake Boost Pressure.


      Powertrain > Stop and Start > Data List
      Tester Display
      Brake Boost Pressure

    8. While depressing the brake pedal several times, check that the Brake Boost Pressure value changes.

    9. Check that DTCs are not output.

      Click here


      Powertrain > Stop and Start > Trouble Codes

  2. STOP AND START SYSTEM OPERATION CHECK

    Tech Tips

    If the cable is disconnected from the negative (-) battery terminal, stop and start control is prohibited until refresh charge is completed. In this case, drive the vehicle approximately 5 to 40 minutes until refresh charge is completed and stop and start control operation is permitted.


    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. Stop the vehicle, move the shift lever to neutral and release the clutch pedal. (for Manual Transaxle)

    5. Depress the brake pedal and stop the vehicle. (for CVT)

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

    7. Depress the clutch pedal and start the engine. (for Manual Transaxle)

    8. Release the brake pedal with the shift lever in D to start the engine. (for CVT)

WIRING DIAGRAM

A01TAQ9E03
*a Vacuum Sensor Assembly
*b Engine Stop and Start ECU

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, perform deceleration sensor zero point clear and calibration.

    Click here

Tech Tips

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.

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PROCEDURE


  1. INSPECT VACUUM SENSOR ASSEMBLY


    1. Inspect the vacuum sensor assembly.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE VACUUM SENSOR ASSEMBLY Click here

    OK

  2. CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - VACUUM SENSOR ASSEMBLY)


    1. Disconnect the A9 engine stop and start ECU connector.

    2. Disconnect the A98 vacuum sensor assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A9-13 (PB) - A98-2 (PB) Always Below 1 Ω
      A9-14 (BRVC) - A98-3 (VC) Always Below 1 Ω
      A9-3 (BRE2) - A98-1 (E2) Always Below 1 Ω
      A9-13 (PB) - Body ground Always 10 kΩ or higher
      A9-14 (BRVC) - Body ground Always 10 kΩ or higher
      A9-3 (BRE2) - Body ground Always 10 kΩ or higher
      A98-2 (PB) - Body ground Always 10 kΩ or higher
      A98-3 (VC) - Body ground Always 10 kΩ or higher
      A98-1 (E2) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE ENGINE STOP AND START ECU Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR