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.

A01VJ4HE04
DTC No. DTC Detection Condition Trouble Area
P1540

The following condition continues for 2 seconds or more (1 trip detection logic):


  • Open or short in vacuum sensor circuit.

  • Ignition switch ON.

  • Wire harness or connector

  • Vacuum sensor assembly

  • Engine stop and start ECU

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. After troubleshooting, perform the following steps to recheck for DTCs.

    Tech Tips


    • If 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 refresh charge is completed and stop and start control is permitted (approximately 15 to 40 minutes).

    • 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. for Manual transaxle


      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 warm it up.

      5. 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.

      6. Stop the vehicle, move the shift lever to neutral and release the clutch pedal.

      7. Keep the engine stopped by stop and start control for 1 second or more.

      8. Depress the clutch pedal and start the engine.

        Tech Tips

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

      9. Check that DTCs are not output Click here.

    2. for CVT


      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 warm it up.

      5. 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.

      6. Depress the brake pedal and stop the vehicle.

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

      8. 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 battery voltage is low.

      9. Check that DTCs are not output Click here.

  2. Check if the stop and start system operates normally.

    Tech Tips

    If 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 refresh charge is completed and stop and start control is permitted (approximately 15 to 40 minutes).


    1. for Manual transaxle


      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.

    2. for CVT


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

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

WIRING DIAGRAM

A01VEZTE29
*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


  • 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. INSPECT VACUUM SENSOR ASSEMBLY


    1. Inspect the vacuum sensor assembly Click here.


    NG

    REPLACE VACUUM SENSOR ASSEMBLY Click here

    OK

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


    1. Disconnect the A92 engine stop and start ECU connector.

    2. Disconnect the A33 vacuum sensor assembly connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A92-13 (PB) - A33-2 (PB) Always Below 1 Ω
      A92-14 (BRVC) - A33-3 (VC) Always Below 1 Ω
      A92-3 (BRE2) - A33-1 (E2) Always Below 1 Ω
      A92-13 (PB) or A33-2 (PB) - Body ground Always 10 kΩ or higher
      A92-14 (BRVC) or A33-3 (VC) - Body ground Always 10 kΩ or higher
      A92-3 (BRE2) or A33-1 (E2) - Body ground Always 10 kΩ or higher

    OK

    REPLACE ENGINE STOP AND START ECU Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR