ECD SYSTEM (w/ EGR Cooler Bypass Valve), Diagnostic DTC:P1271, P1272

DTC Code DTC Name
P1271 Fuel Regulator Circuit Malfunction (EDU Drive)
P1272 Fuel Pressure Regulator Malfunction

DESCRIPTION

The ECM controls the internal fuel pressure of the common rail by opening and closing the pressure discharge valve. When sudden deceleration occurs, the internal fuel pressure will temporarily become higher than usual and combustion noise may result. Therefore the ECM will open the valve temporarily to discharge the excess pressure inside the common rail assembly. Also, the pressure discharge valve opens when the ignition switch is turned off to allow prompt discharge of the common rail internal pressure.

Tech Tips


  • For more information on the pressure discharge valve and the common rail system Click here.

  • For more information on the EDU Click here.

  • If P1271 and/or P1272 is present, refer to the DTC chart for the fuel system Click here.

A01KFZ3E02
A01KEXOE03
DTC No. DTC Detection Condition Trouble Area
P1271

Open or short in pressure discharge valve circuit.

There is no valve opening confirmation (IJf) signal from EDU to ECM despite the ECM sending valve opening command (PRD) signal after the engine is started.

(1 trip detection logic)


  • Open or short in pressure discharge valve circuit

  • Open or short in pressure discharge valve itself

  • EDU

  • ECM

P1272

Pressure discharge valve closed malfunction.

Actual pressure decreasing rate deviates from the simulated pressure decreasing rate after the ignition switch is turned off.

(2 trip detection logic)


  • Open or short in pressure discharge valve circuit (P1271 is set simultaneously)

  • Pressure discharge valve

  • Suction control valve

  • ECM

Tech Tips


  • After confirming DTC P1271 and/or P1272, check the fuel pressure inside the common rail assembly in the "Powertrain / Engine and ECT / Data List / Fuel Press" using the intelligent tester.

  • P1271:

    After clearing the DTC, drive the vehicle at 50 km/h (31 mph) with the third gear and then decelerate by releasing the accelerator pedal. Check that P1271 is not present.

  • P1272:

    After clearing the DTC, start and stop the engine twice, and then confirm that P1272 is not present.

Standard
Engine Speed Fuel Pressure
Idling Approximately 30,000 to 40,000 kPa
3,000 rpm (No engine load) Approximately 45,000 to 90,000 kPa

MONITOR DESCRIPTION

P1271 (Open or short in pressure discharge valve circuit):

This DTC will be set if there is no valve opening confirmation (IJf) signal sent from the EDU to the ECM even though the ECM has commanded the EDU to open the pressure discharge valve. This DTC refers to an open or short circuit malfunction of the pressure discharge valve circuit, not a malfunction that includes a valve that is stuck open or closed.

The EDU monitors the current supplied to the pressure discharge valve to verify that the current flows into the valve. If the current exceeds the specified level, the EDU determines that the IJf signal is low. If this DTC is present, the enters the fail-safe mode and limits ECM engine power. The fail-safe mode continues until the ignition switch is turned off.

A01KHZCE05
P1272 (Closed malfunction of the pressure discharge valve):

The pressure discharge valve will open and discharge the internal fuel pressure from the common rail assembly to the fuel tank sub-assembly when the ignition switch is turned off. In this event, the ECM compares the actual drop rate of the internal fuel pressure and the target drop rate. If the ECM judges the actual drop rate is smaller than the target, the ECM then judges that the valve has stuck closed and sets this DTC. This DTC will be stored if the internal fuel pressure does not drop to the target after the ignition switch has been turned off.

If this DTC is present, the ECM enters fail-safe mode and limits the engine power. The fail-safe mode continues until the ignition switch is turned off.

WIRING DIAGRAM

A01KFKXE02

INSPECTION PROCEDURE

Note

After replacing the ECM, the new ECM needs registration Click here and initialization Click here.

Tech Tips


  • After completing repairs, confirm that P1271 and/or P1272 does not recur.

  • If P0200 and P1271 are present simultaneously, there is an open circuit in the INJF wire harness between the EDU and ECM, or in the wire harness for both fuel injector assembly and pressure discharge valve.

PROCEDURE


  1. CHECK DTC OUTPUT (DTC P1271 AND/OR P1272)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON and turn the tester on.

    3. Select the following menus: Powertrain / Engine and ECT / DTC.

    4. Read DTCs.

      Result
      Display (DTC output) Proceed to
      P1271 or P1271 and P1272 A
      P1272 B

    B
    A
  2. INSPECT COMMON RAIL ASSEMBLY (PRESSURE DISCHARGE VALVE)


    1. A01KHG9E04
      Text in Illustration
      *1 Pressure Discharge Valve Connector
      *a Component Side
      *b Front View

      Disconnect the P9 pressure discharge valve connector.

    2. Measure the resistance between the terminals of the pressure discharge valve.

      Standard resistance
      Tester Connection Condition Specified Condition
      1 - 2 20°C (68°F) 0.85 to 1.05 Ω
    3. Reconnect the pressure discharge valve connector.


    NG
    OK
  3. CHECK HARNESS AND CONNECTOR (PRESSURE DISCHARGE VALVE - EDU)


    1. Disconnect the E9 and E14 EDU connectors.

    2. Disconnect the P9 pressure discharge valve connector.

    3. Check the resistance.

      Standard resistance (Check for open)
      Tester Connection Specified Condition
      E9-3 (RLF+) - P9-1 (RLV) Below 1 Ω
      E14-4 (RLF-) - P9-2 (COM3) Below 1 Ω
      Standard resistance (Check for short)
      Tester Connection Specified Condition
      E9-3 (RLF+) or P9-1 (RLV) - Body ground 10 kΩ or higher
      E14-4 (RLF-) or P9-2 (COM3) - Body ground 10 kΩ or higher
    4. Reconnect the EDU connectors.

    5. Reconnect the pressure discharge valve connector.


    NG
    OK
  4. CHECK HARNESS AND CONNECTOR (ECM - EDU)


    1. Disconnect the E15 EDU connector.

    2. Disconnect the E13 ECM connector.

    3. Check the resistance.

      Standard resistance (Check for open)
      Tester Connection Specified Condition
      E15-2 (PRD) - E13-19 (PRD) Below 1 Ω
      Standard resistance (Check for short)
      Tester Connection Specified Condition
      E15-2 (PRD) or E13-19 (PRD) - Body ground 10 kΩ or higher
    4. Reconnect the EDU connector.

    5. Reconnect the ECM connector.


    NG
    OK
  5. INSPECT EDU (POWER SOURCE CIRCUIT)


    1. A01KHJKE02
      Text in Illustration
      *1 EDU Connector
      *a Wire Harness Side

      Disconnect the E14 EDU connector.

    2. Turn the ignition switch to ON.

    3. Measure the voltage between the specified terminals of the EDU connector.

      Standard voltage
      Tester Connection Specified Condition
      E14-2 (+B) - E14-3 (GND) 11 to 14 V
    4. Reconnect the EDU connector.


    NG
    OK
  6. INSPECT ECM (PRD VOLTAGE)


    1. A01KECRE02
      Text in Illustration
      *1 ECM Connector

      Inspect the ECM using the oscilloscope.

    2. Drive the vehicle at 50 km/h (31 mph) with the third gear, and then decelerate by releasing the accelerator pedal.

    3. Check the waveform between the terminals of the E13 and E10 ECM connectors.

      Standard
      Tester Connection Specified Condition
      E13-19 (PRD) - E10-1 (E1) Correct waveform shown

      Tech Tips

      Alternative inspection:

      Run the engine at 2,500 rpm for 10 seconds and then decrease the engine speed to idling by completely releasing the accelerator pedal.


    NG
    OK
  7. REPLACE INJECTOR DRIVER (EDU)


    1. Replace the injector driver (EDU) Click here.


    NEXT
  8. CHECK WHETHER DTC OUTPUT RECURS (SEE IF DTC IS OUTPUT AGAIN)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON and turn the tester on.

    3. Clear DTCs Click here.

    4. Start the engine.

      Tech Tips

      P1271:

      After clearing the DTC, drive the vehicle at 50 km/h (31 mph) with the third gear and then decelerate by releasing the accelerator pedal. Confirm that DTC P1271 is not present again.

      P1272:

      After clearing the DTC, start and stop the engine twice, and then confirm that DTC P1272 is not present again.

    5. Select the following menus: Powertrain / Engine and ECT / DTC.

    6. Read DTCs.

      Result
      Display (DTC output) Proceed to
      P1271 and/or P1272 A
      No output B

    B
    A
  9. REPLACE COMMON RAIL ASSEMBLY


    1. Replace the common rail assembly Click here.


    NEXT
  10. CHECK WHETHER DTC OUTPUT RECURS

    Tech Tips

    P1271:

    After clearing the DTC, drive the vehicle at 50 km/h (31 mph) with the third gear and then decelerate by releasing the accelerator pedal. Confirm that DTC P1271 is not present again.

    P1272:

    After clearing the DTC, start and stop the engine twice, and then confirm that DTC P1272 is not present again.


    NEXT