Dtc P1271 Fuel Regulator Circuit Malfunction (Edu Drive)

Engine. Lexus Is250, Is220D. Gse20 Ale20
2Ad-Fhv Engine Control System. Lexus Is250, Is220D. Gse20 Ale20

DESCRIPTION

MONITOR DESCRIPTION

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

WIRING DIAGRAM

INSPECTION PROCEDURE

READ DTC OUTPUT

INSPECT COMMON RAIL ASSEMBLY (PRESSURE DISCHARGE VALVE)

CHECK HARNESS AND CONNECTOR (PRESSURE DISCHARGE VALVE - EDU)

CHECK HARNESS AND CONNECTOR (ECM - EDU)

INSPECT EDU (POWER SOURCE CIRCUIT)

REPLACE EDU

CHECK IF DTC OUTPUT RECURS (SEE IF DTC IS OUTPUT AGAIN)

REPLACE COMMON RAIL ASSEMBLY

DTC P1271 Fuel Regulator Circuit Malfunction (EDU Drive)

DTC 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. Also, the pressure discharge valve opens when the engine switch is turned OFF to allow prompt discharge of the common rail internal pressure.
HINT:
  1. For more information on the pressure discharge valve and the common rail system (Click here).
  2. For more information on the EDU (Click here).
  3. If P1271 and/or P1272 is present, refer to the DTC chart for the fuel system (Click here).

Lexus Is250, Is220D. Gse20 Ale20.2Ad-Fhv Engine Control System.Ecd System. Dtc P1271 Fuel Regulator Circuit Malfunction (Edu Drive)


Lexus Is250, Is220D. Gse20 Ale20.2Ad-Fhv Engine Control System.Ecd System. Dtc P1271 Fuel Regulator Circuit Malfunction (Edu Drive)


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)
  1. Open or short in pressure discharge valve circuit
  2. Open or short in pressure discharge valve itself
  3. EDU
  4. ECM
P1272
Pressure discharge valve closed malfunction.
Actual pressure decreasing rate deviates from the simulated pressure decreasing rate after the engine switch is turned OFF.
(2 trip detection logic)
  1. Open or short in pressure discharge valve circuit (P1271 is set simultaneously)
  2. Pressure discharge valve
  3. Supply pump
  4. ECM

HINT:
  1. After confirming DTC P1271 and/or P1272, check the fuel pressure inside the common rail in the "Powertrain / Engine / Data List / Fuel Press" using the intelligent tester.
  2. 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.
  3. P1272:
    After clearing the DTC, start and stop the engine twice, and then confirm that P1272 is not present.

Reference:
Engine Speed
Fuel Pressure (MPa)
Idling
Approximately 37 to 43
2,500 rpm (No engine load)
Approximately 60 to 66

MONITOR DESCRIPTION

  1. 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 engine switch is turned OFF.

    Lexus Is250, Is220D. Gse20 Ale20.2Ad-Fhv Engine Control System.Ecd System. Dtc P1271 Fuel Regulator Circuit Malfunction (Edu Drive)

  1. 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 engine 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 engine 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 engine switch is turned OFF.

MONITOR STRATEGY


P1271:
Required sensors
EDU
Frequency of operation
Continuous
Duration
3 seconds
CHK ENG operation
1 driving cycle

P1272:
Required sensors
Fuel pressure sensor
Frequency of operation
Once per driving cycle
Duration
1 second
CHK ENG 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
30 MPa (306 kgf/cm2, 4,351 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 is 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 engine switch was turned OFF

WIRING DIAGRAM


Lexus Is250, Is220D. Gse20 Ale20.2Ad-Fhv Engine Control System.Ecd System. Dtc P1271 Fuel Regulator Circuit Malfunction (Edu Drive)


INSPECTION PROCEDURE

NOTICE:
After replacing the ECM, the new ECM needs registration (Click here) and initialization (Click here).
HINT:
  1. After completing repairs, confirm that P1271 and/or P1272 does not recur.
  2. 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.
1.READ DTC OUTPUT

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch ON (IG) and turn the intelligent tester ON.

  1. Enter the following menus: "Powertrain / Engine / DTC".

  1. Read DTCs.

    Result:

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


B
Go to step 8
A


2.INSPECT COMMON RAIL ASSEMBLY (PRESSURE DISCHARGE VALVE)


    Lexus Is250, Is220D. Gse20 Ale20.2Ad-Fhv Engine Control System.Ecd System. Dtc P1271 Fuel Regulator Circuit Malfunction (Edu Drive)

  1. Disconnect the E68 pressure discharge valve connector.

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

    Standard resistance:
    Condition
    		Specified Condition
    20°C (68°F)
    		0.85 to 1.05 Ω

  1. Reconnect the pressure discharge valve connector.



NG
REPLACE COMMON RAIL ASSEMBLY
OK


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


    Lexus Is250, Is220D. Gse20 Ale20.2Ad-Fhv Engine Control System.Ecd System. Dtc P1271 Fuel Regulator Circuit Malfunction (Edu Drive)

  1. Disconnect the E84 EDU connector.

  1. Disconnect the E68 pressure discharge valve connector.

  1. Check the resistance between the wire harness side connectors.

    Standard resistance (Check for open):
    Tester Connection
    		Specified Condition
    RLF+ (E84-3) - (E68-2)
    		Below 1 Ω
    RLF- (E84-6) - (E68-1)
    		Below 1 Ω
    Standard resistance (Check for short):
    Tester Connection
    		Specified Condition
    RLF+ (E84-3) or - (E68-2) - Body ground
    		10 kΩ or higher
    RLF- (E84-6) or (E68-1) - Body ground
    		10 kΩ or higher

  1. Reconnect the EDU connector.

  1. Reconnect the pressure discharge valve connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


4.CHECK HARNESS AND CONNECTOR (ECM - EDU)


    Lexus Is250, Is220D. Gse20 Ale20.2Ad-Fhv Engine Control System.Ecd System. Dtc P1271 Fuel Regulator Circuit Malfunction (Edu Drive)

  1. Disconnect the E85 EDU connector.

  1. Disconnect the E59 ECM connector.

  1. Check the resistance between the wire harness side connectors.

    Standard resistance (Check for open):
    Tester Connection
    		Specified Condition
    PRD (E85-7) - PRD (E59-52)
    		Below 1 Ω
    Standard resistance (Check for short):
    Tester Connection
    		Specified Condition
    PRD (E85-7) or PRD (E59-52) - Body ground
    		10 kΩ or higher

  1. Reconnect the EDU connector.

  1. Reconnect the ECM connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


5.INSPECT EDU (POWER SOURCE CIRCUIT)


    Lexus Is250, Is220D. Gse20 Ale20.2Ad-Fhv Engine Control System.Ecd System. Dtc P1271 Fuel Regulator Circuit Malfunction (Edu Drive)

  1. Disconnect the E86 EDU connector.

  1. Turn the engine switch ON (IG).

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

    Standard voltage:
    Tester Connection
    		Specified Condition
    +B (E86-3) - GND (E86-2)
    		9 to 14 V

  1. Reconnect the EDU connector.



NG
CHECK EDU POWER SOURCE CIRCUIT (EDU - BATTERY)
OK


6.REPLACE EDU

NEXT


7.CHECK IF DTC OUTPUT RECURS (SEE IF DTC IS OUTPUT AGAIN)

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch ON (IG) and turn the tester ON.

  1. Clear DTCs.

  1. Start the engine.

  1. Enter the following menus: Powertrain / Engine / DTC.

  1. Read the DTCs using the intelligent tester.

    Result:

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


B
SYSTEM IS OK
A

REPLACE ECM

8.REPLACE COMMON RAIL ASSEMBLY

NEXT

CHECK IF DTC OUTPUT RECURS