DTC    P1540    Brake Booster Sensor Circuit (Open or Short)


DESCRIPTION

This description and the following Inspection Procedure are for DTC P1540 which is stored in the engine stop and start ECU. The vacuum sensor assembly detects the brake booster pressure and represents it as a voltage value. The vacuum sensor assembly detects the absolute pressure inside the brake booster.
If an open or short in the circuit is detected based on the output voltage of the vacuum sensor assembly, this DTC will be stored.

A199263E01


DTC No.
DTC Detection Condition
Trouble Area
P1540
The following condition continues for 2 seconds or more (1 trip detection logic):
  1. Open or short in vacuum sensor circuit.
  1. Harness or connector
  2. Vacuum sensor assembly
  3. Engine stop and start ECU

HINT:
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).


After troubleshooting, perform the following steps to recheck for DTCs and check if the Stop and Start system operates normally.

HINT:
  1. If the ECM learned values have been cleared by disconnecting the battery or for another reason, Stop and Start system control will be prohibited until ECM learning completes.
  2. 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 intelligent tester to the DLC3.

  2. Clear the DTCs (Click here).

  3. Start the engine and allow it to idle.

  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).


Check if the Stop and Start system operates normally.

HINT:
If the battery terminal has been disconnected, the ECO OFF indicator will be illuminated. In this case, drive the vehicle for 15 to 40 minutes to turn off the indicator.

  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.

  4. Stop the vehicle. Move the shift lever to neutral and release the clutch pedal.

  5. Check that the engine stops.

  6. Depress the clutch pedal and check that the engine restarts.


WIRING DIAGRAM


A217710E01


INSPECTION PROCEDURE

NOTICE:
  1. 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).
  2. 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).

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 engine stop and start ECU connector.

  1. Disconnect the vacuum sensor assembly connector.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    D79-11 (PB) - U1-2 (PB)
    		Always
    		Below 1 Ω
    D79-19 (VC) - U1-3 (VC)
    		Always
    		Below 1 Ω
    D79-24 (E2) - U1-1 (E2)
    		Always
    		Below 1 Ω
    D79-11 (PB) or U1-2 (PB) - Body ground
    		Always
    		10 kΩ or higher
    D79-19 (VC) or U1-3 (VC) - Body ground
    		Always
    		10 kΩ or higher
    D79-24 (E2) or U1-1 (E2) - Body ground
    		Always
    		10 kΩ or higher

  1. Reconnect the engine stop and start ECU connector and vacuum sensor assembly connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE ENGINE STOP AND START ECU (Click here)