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STOP AND START SYSTEM, Diagnostic DTC:P1541

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DTC Code DTC Name
P1541 Brake Booster Sensor Circuit
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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 input value from the vacuum sensor assembly remains the same even though the brake booster assembly pressure changes when the brake pedal is operated or the vehicle is being driven, the engine stop and start ECU judges that the sensor is stuck.

When sticking of the sensor is detected, the engine stop and start ECU stores DTC P1541 and blinks the stop and start cancel indicator light.

DTC No. DTC Detection Condition Trouble Area
P1541

The following condition is met (1 trip detection logic):


  • Vacuum does not change while brake pedal is operated 3 times in a row.

Both of the following conditions are met (1 trip detection logic):


  • Vehicle speed exceeds 30 km/h (18.6 mph) 30 times or more.

  • Changes in vacuum (difference between the maximum and minimum values) is 0.3 kPa (2 mmHg, 0.09 in.Hg) or less.

  • Vacuum sensor assembly

  • Brake booster assembly

  • Check valve to connector tube hose (brake booster hose)

  • Engine stop and start ECU
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CONFIRMATION DRIVING PATTERN

Tip:

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).


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  1. CONFIRMATION AFTER TROUBLESHOOTING

    Tip:

    • When the cable is disconnected from the negative (-) battery terminal, stop and start control is prohibited for a certain amount of time. After connecting the cable, drive the vehicle until stop and start control is permitted (approximately 15 to 40 minutes).

    • Allow the engine to idle for 3 minutes after the engine warms up and check that the engine 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).

    4. Start the engine and warm it up.

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

    6. Drive the vehicle at 30 km/h (18.6 mph) or more and stop the vehicle. Repeat this driving pattern 30 times to allow the brake booster vacuum to change.

    7. Stop the vehicle.

    8. Check that DTCs are not output (Click here).

  2. STOP AND START SYSTEM OPERATION CHECK

    Tip:

    When the cable is disconnected from the negative (-) battery terminal, stop and start control is prohibited for a certain amount of time. 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 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.

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WIRING DIAGRAM

Refer to DTC P1540 (Click here).

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INSPECTION PROCEDURE

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).

Tip:

  • 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).

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PROCEDURE


  1. Click here

    CHECK ANY OTHER DTCS 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. Read the other DTCs.

      Table 1. Result
      Result Proceed to
      Other DTCs are not output A
      Other DTCs are output B

  2. Click here

    READ VALUE USING GTS (BRAKE BOOST PRESSURE)


    1. Start the engine and warm it up.

    2. Turn the ignition switch off.

    3. Turn the ignition switch to ON.

    4. Turn the GTS on.

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

    6. Depress the brake pedal 5 times and read the changes in the following pressure value.

      Table 2. Stop and Start
      GTS Display Measurement Item/Range Normal Condition Diagnostic Note
      Brake Boost Pressure

      Brake booster pressure (absolute pressure)/

      Min.: -640 kPa(abs) (-4800 mmHg, -188 in.Hg), Max.: 112 kPa(abs) (840 mmHg, 33.0 in.Hg)

      		 Approx. 100 kPa (750 mmHg, 29.5 in.Hg): Ignition switch ON, brake pedal depressed several times (differs according to atmospheric pressure) -
      OK
      Changes by 20 kPa (150 mmHg, 5.91 in.Hg) or higher

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    INSPECT CHECK VALVE TO CONNECTOR TUBE HOSE (BRAKE BOOSTER HOSE)


    1. Visually check the check valve to connector tube hose (brake booster hose) for cracks or clogging.

      OK
      No cracks or clogging in the check valve to connector tube hose (brake booster hose).

  4. Click here

    REPLACE VACUUM SENSOR ASSEMBLY


    1. Replace the vacuum sensor assembly (Click here).


  5. Click here

    CLEAR DTC


    1. Connect the GTS to the DLC3.

    2. Turn the GTS on.

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

    4. Clear the DTC.


  6. Click here

    CHECK DTC OUTPUT


    1. Start the engine and warm it up.

    2. Turn the GTS on.

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

    4. Drive the vehicle at 30 km/h (18.6 mph) or more and stop the vehicle. Repeat this driving pattern 30 times to allow the brake booster vacuum to change.

    5. Stop the vehicle.

    6. Check that no DTCs are output (Click here).

      Table 3. Result
      Result Proceed to
      DTC is not output A
      DTC is output B

  7. Click here

    GO TO DIAGNOSTIC TROUBLE CODE CHARTClick here

  8. Click here

    USE SIMULATION METHOD TO CHECKClick here

  9. Click here

    REPLACE CHECK VALVE TO CONNECTOR TUBE HOSE

  10. Click here

    END

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    REPLACE ENGINE STOP AND START ECUClick here