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.

A004Q2ME17
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

  • Ignition switch is turned to ON

  • 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. CONFIRMATION AFTER TROUBLESHOOTING


    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.

    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.

    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 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 the 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.

    5. Allow the engine to stop by stop and start control.

    6. Depress the clutch pedal and start the engine.

WIRING DIAGRAM

A004S08E40
*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 yaw rate sensor, 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 Click here.

PROCEDURE


  1. CHECK VACUUM SENSOR ASSEMBLY (PB TERMINAL VOLTAGE)

    A004Q17E02
    Text in Illustration
    *a

    Component with harness connected

    (Engine Stop and Start ECU)

    		 - -

    1. Turn the ignition switch to ON.

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

      Standard Voltage
      Tester Connection Switch Condition Result Proceed to
      A80-13 (PB) - A80-3 (BRE2) Ignition switch ON 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 A80 engine stop and start ECU connector.

    2. Disconnect the A81 vacuum sensor assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A80-13 (PB) - A81-2 (PB) Always Below 1 Ω
      A80-14 (BRVC) - A81-3 (VC) Always Below 1 Ω
      A80-3 (BRE2) - A81-1 (E2) Always Below 1 Ω
      A80-13 (PB) - Body ground Always 10 kΩ or higher
      A80-14 (BRVC) - Body ground Always 10 kΩ or higher
      A80-3 (BRE2) - Body ground Always 10 kΩ or higher
      A81-2 (PB) - Body ground Always 10 kΩ or higher
      A81-3 (VC) - Body ground Always 10 kΩ or higher
      A81-1 (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)

    A004T7RE02
    Text in Illustration
    *a

    Component with harness connected

    (Engine Stop and Start ECU)

    		 - -

    1. Turn the ignition switch to ON.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A80-14 (BRVC) - A80-3 (BRE2) Ignition switch ON 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 ignition switch to ON.

    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