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.

A280541E02

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

Tip:

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.

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

      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

    Tip:

    When the cable is disconnected from the negative (-) battery terminal, stop and start control is prohibited until refresh charge is completed. After connecting the cable, drive the vehicle until stop and start control is permitted (approximately 15 to 40 minutes).

    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.

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

    6. Depress the clutch pedal to start the engine.

WIRING DIAGRAM

A285528E14

CAUTION / NOTICE / HINT

Note:

  • Before replacing the engine stop and start ECU, download the current status (number of starter operations) and upload it into a new engine stop and start ECU.

    Click here

  • After replacing the engine stop and start ECU or air conditioning control assembly, initialize 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

Tip:

  • 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.

    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 hereClick here

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 A24 engine stop and start ECU connector.

    2. Disconnect the A15 vacuum sensor assembly connector.

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

      Standard Resistance

      Tester Connection

      Condition

      Specified Condition

      A24-13 (PB) - A15-2 (PB)

      Always

      Below 1 Ω

      A24-14 (BRVC) - A15-3 (VC)

      Always

      Below 1 Ω

      A24-3 (BRE2) - A15-1 (E2)

      Always

      Below 1 Ω

      A24-13 (PB) - Body ground

      Always

      10 kΩ or higher

      A24-14 (BRVC) - Body ground

      Always

      10 kΩ or higher

      A24-3 (BRE2) - Body ground

      Always

      10 kΩ or higher

      A15-2 (PB) - Body ground

      Always

      10 kΩ or higher

      A15-3 (VC) - Body ground

      Always

      10 kΩ or higher

      A15-1 (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