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

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

DESCRIPTION

Tech Tips


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

  • For more information on the injection driver (EDU) Click here.

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

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. Also, the pressure discharge valve opens when the ignition switch is turned OFF to allow prompt discharge of the common rail internal pressure.

A01DUZBE01
A01DWWKE01
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

  • Supply pump

  • ECM

Tech Tips

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

Reference
Engine Speed Fuel Pressure
Idling Approximately 28000 to 40000 kPa
3000 rpm (No engine load) Approximately 30000 to 60000 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 ECM enters the fail-safe mode and limits engine power. The fail-safe mode continues until the ignition switch is turned OFF.

A01E1Y8E02
P1272 (Closed malfunction of the pressure discharge valve):

The pressure discharge valve will open and discharge the internal fuel pressure from the common rail to the fuel tank when the ignition switch is turned OFF. When this occurs, 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 is 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 a fail-safe mode and limits engine power. The fail-safe mode continues until the ignition switch is turned OFF.

PULSE GENERATION INSPECTION

Tech Tips

The problem area can be identified by checking the waveform at the following terminals.

A01DWJSE03

Tech Tips

A and D are on the ECM side, and B and C are on the EDU side.

Malfunction Point Trouble Area
A

  • ECM
B (If A is normal)

  • Open or short in "PRD (ECM)" - "PRD (EDU)" circuit
C (If A and B are normal)

  • Open or short in "RLF+ (EDU)" - "RLF- (EDU)" circuit

  • Pressure discharge valve

  • EDU
D (If A, B and C are normal)

  • Open or short in "INJF (EDU)" - "INJF (ECM)" circuit (P0200 is set simultaneously)

MONITOR STRATEGY

P1271:
Required sensor EDU
Frequency of operation Continuous
Duration 3 seconds
MIL operation 1 driving cycle
P1272:
Required sensors Fuel pressure sensor
Frequency of operation Once per driving cycle
Duration 1 second
MIL operation 2 driving cycles

TYPICAL ENABLING CONDITIONS

P1271:
Specification
Drive the vehicle at 50 km/h (31 mph) in 3rd gear and then decelerate by completely releasing the accelerator pedal
P1272:
Item Specification
Minimum Maximum
Fuel pressure

27000 kPa (275 kgf/cm2, 3915 psi)

 -
Fuel temperature 0°C (32°F) -
Battery voltage 11 V -
The monitor will not run if the fuel pressure sensor, pressure discharge valve circuit, or fuel temperature sensor is malfunctioning

TYPICAL MALFUNCTION THRESHOLDS

P1271:
Specification
There are no confirmation signals from the EDU, despite the ECM sending the command signals regularly during deceleration
P1272:
Specification
The internal pressure stays beyond the specified level after the ignition switch was turned OFF

WIRING DIAGRAM

A01E2U9E24

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 injector and pressure discharge valve.

  • Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, and other data from the time the malfunction occurred.

PROCEDURE


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


    1. Connect the intelligent tester to the DLC3.

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

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

    4. Read DTCs.

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

    B

    REPLACE COMMON RAIL ASSEMBLY (PRESSURE DISCHARGE VALVE) Click here

    A

  2. INSPECT COMMON RAIL ASSEMBLY (PRESSURE DISCHARGE VALVE)


    1. A01DZRYE11

      Disconnect the pressure discharge valve connector.

    2. Measure the resistance of the pressure discharge valve.

      Standard resistance
      Tester Connection Condition Specified Condition
      1 - 2 20°C (68°F) 0.85 to 1.05 Ω

    NG

    REPLACE COMMON RAIL ASSEMBLY Click here

    OK

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


    1. A01DXPNE20

      w/o EGR System


      1. Disconnect the I17 and I18 EDU connectors.

      2. Disconnect the P20 pressure discharge valve connector.

      3. Measure the resistance of the wire harness side connectors.

        Standard resistance
        Tester Connection Specified Condition
        RLF+ (I17-4) - P20-2 Below 1 Ω
        RLF- (I18-1) - P20-1 Below 1 Ω
        RLF+ (I17-4) or P20-2 - Body ground 10 kΩ or higher
        RLF- (I18-1) or P20-1 - Body ground 10 kΩ or higher

    2. w/ EGR System


      1. Disconnect the I17 and I18 EDU connectors.

      2. Disconnect the P22 pressure discharge valve connector.

      3. Measure the resistance of the wire harness side connectors.

        Standard resistance
        Tester Connection Specified Condition
        RLF+ (I17-4) - P22-2 Below 1 Ω
        RLF- (I18-1) - P22-1 Below 1 Ω
        RLF+ (I17-4) or P22-2 - Body ground 10 kΩ or higher
        RLF- (I18-1) or P22-1 - Body ground 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. CHECK HARNESS AND CONNECTOR (ECM - EDU)


    1. A01E1Y1E02

      Disconnect the I19 EDU connectors.

    2. Disconnect the E8 ECM connector.

    3. Measure the resistance of the wire harness side connectors.

      Standard resistance
      Tester Connection Specified Condition
      PRD (E8-32) - PRD (I19-2) Below 1 Ω
      INJF (E8-25) - INJF (I19-5) Below 1 Ω
      PRD (E8-32) or PRD (I19-2) - Body ground 10 kΩ or higher
      INJF (E8-25) or INJF (I19-5) - Body ground 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  5. INSPECT INJECTOR DRIVER (BATTERY VOLTAGE)


    1. A01DX1JE01

      Disconnect the I17 EDU connector.

    2. Turn the ignition switch ON.

    3. Measure the voltage of the EDU connector.

      Standard voltage
      Tester Connection Specified Condition
      +B (I17-2) - GND (I17-3) 11 to 14 V

    NG

    CHECK INJECTOR DRIVER POWER SOURCE CIRCUIT (EDU - BATTERY)

    OK

  6. INSPECT ECM (PRD VOLTAGE)

    A01DY3AE04

    1. Inspect the ECM using the oscilloscope.

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

    3. Check the waveform between the terminal of the E7 and E8 ECM connectors.

      Standard
      Tester Connection Specified Condition
      PRD (E8-32) - E1 (E7-7) Correct waveform shown

      Tech Tips

      Alternative inspection:

      Run the engine at 2500 rpm for 10 seconds and then decrease the engine speed to idling by completely releasing the accelerator pedal.


    NG

    REPLACE ECM Click here

    OK

  7. REPLACE INJECTOR DRIVER


    1. Replace the injector driver Click here.


    NEXT

  8. CHECK IF DTC OUTPUT RECURS (DTC P1271 AND/OR P1272)

    Tech Tips

    P1271:

    After clearing the DTC, drive the vehicle at 50 km/h (31 mph) in 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

    END

  9. REPLACE COMMON RAIL ASSEMBLY (PRESSURE DISCHARGE VALVE)


    1. Replace common rail assembly Click here.


    NEXT

  10. CHECK IF DTC OUTPUT RECURS (DTC P1271 AND/OR P1272)

    Tech Tips

    P1271:

    After clearing the DTC, drive the vehicle at 50 km/h (31 mph) in 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

    END