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.

A005H8SE03
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.

  • Harness or connector

  • Vacuum sensor assembly

  • Engine stop and start ECU

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 battery terminal has been disconnected, the stop and start will be prohibited. In this case, drive the vehicle for 15 to 40 minutes to permit the stop and start operation.

    • 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. Clear the DTCs Click here.

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

    4. Stop the engine and turn the ignition switch to ON.

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

    6. While depressing the brake pedal several times, check that the Brake Boost Pressure value changes.

    7. Check that no DTCs are output Click here.

  2. Check if the Stop and Start system operates normally.

    Tech Tips

    If the battery terminal has been disconnected, the stop and start will be prohibited. In this case, drive the vehicle for 15 to 40 minutes to permit the stop and start operation.


    1. Warm up the engine.

    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, allow the engine to stop due to stop and start system control (with the shift lever in D).

    5. Release the brake pedal to allow the engine to restart (with the shift lever in D).

    6. Release the brake pedal and check that the engine restarts.

WIRING DIAGRAM

A005MG2E03
*a Vacuum Sensor Assembly
*b Engine Stop and Start ECU

CAUTION / NOTICE / HINT

Note


  • If the engine stop and start ECU is being replaced, register the previously recorded number of starter operations into the new engine stop and start ECU Click here.

  • After the engine stop and start ECU is replaced or after an air conditioner kit is installed, clear the A/C information stored in the engine stop and start ECU Click here.

  • After the engine stop and start ECU or airbag sensor assembly (yaw rate sensor) is replaced, initialize and calibrate 0 point of deceleration sensor 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 A73 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
      A73-13 (PB) - A33-2 (PB) Always Below 1 Ω
      A73-14 (BRVC) - A33-3 (VC) Always Below 1 Ω
      A73-3 (BRE2) - A33-1 (E2) Always Below 1 Ω
      A73-13 (PB) or A33-2 (PB) - Body ground Always 10 kΩ or higher
      A73-14 (BRVC) or A33-3 (VC) - Body ground Always 10 kΩ or higher
      A73-3 (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