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.

A01W167E12
DTC No. DTC Detection Condition Trouble Area
P1540

The following conditions continue for 2 seconds or more (1 trip detection logic):


  • Open or short in vacuum sensor assembly circuit

  • Engine switch on (IG)

  • Vacuum sensor assembly

  • Engine stop and start ECU

  • Wire harness or connector

CONFIRMATION DRIVING PATTERN

Tech Tips

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.


  1. 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 60 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.

    CONFIRMATION AFTER TROUBLESHOOTING


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG) and turn the GTS on.

    3. Clear the DTCs Click here.

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

    5. Stop the engine and turn the engine switch on (IG).

    6. Turn the GTS on.

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

  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 60 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 the 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

A01W1QZE31
*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, clear and calibrate the deceleration sensor zero point in the engine stop and start ECU 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 Click here.

PROCEDURE


  1. CHECK VACUUM SENSOR ASSEMBLY (PB TERMINAL VOLTAGE)

    A01W0Q0E02
    Text in Illustration
    *a

    Component with harness connected

    (Engine Stop and Start ECU)

    		 - -

    1. Turn the engine switch on (IG).

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

      Standard Voltage
      Tester Connection Switch Condition Result Proceed to
      A77-13 (PB) - A77-3 (BRE2) Engine switch on (IG) Voltage value is 4.7 V or higher, or 0.6 V or lower A
      Voltage value is other than listed above B

    B

    USE SIMULATION METHOD TO CHECK Click here

    A

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


    1. Disconnect the A77 engine stop and start ECU connector.

    2. Disconnect the A78 vacuum sensor assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A77-13 (PB) - A78-2 (PB) Always Below 1 Ω
      A77-14 (BRVC) - A78-3 (VC) Always Below 1 Ω
      A77-3 (BRE2) - A78-1 (E2) Always Below 1 Ω
      A77-13 (PB) - Body ground Always 10 kΩ or higher
      A77-14 (BRVC) - Body ground Always 10 kΩ or higher
      A77-3 (BRE2) - Body ground Always 10 kΩ or higher
      A78-2 (PB) - Body ground Always 10 kΩ or higher
      A78-3 (VC) - Body ground Always 10 kΩ or higher
      A78-1 (E2) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. CHECK ENGINE STOP AND START ECU (BRVC TERMINAL VOLTAGE)

    A01W461E03
    Text in Illustration
    *a

    Component with harness connected

    (Engine Stop and Start ECU)

    		 - -

    1. Turn the engine switch on (IG).

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A77-14 (BRVC) - A77-3 (BRE2) Engine switch on (IG) 4.75 to 5.25 V

    NG

    REPLACE ENGINE STOP AND START ECU Click here

    OK

  4. REPLACE VACUUM SENSOR ASSEMBLY


    1. Replace the vacuum sensor assembly Click here.


    NEXT

  5. CHECK DTC OUTPUT


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Stop and Start / Trouble Codes.

    5. Check that no DTCs are output.

      Result
      Result Proceed to
      DTCs are not output A
      DTC P1540 is output B

    A

    END

    B

    REPLACE ENGINE STOP AND START ECU Click here