ECD SYSTEM, 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. Also, the pressure discharge valve opens when the ignition switch is turned off to allow prompt discharge of the common rail internal pressure and so that the engine stops smoothly.

Tech Tips

For more information on the pressure discharge valve and 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.

Cross Section Diagram of Pressure Discharge Valve
*1	Return to Fuel Tank (Low Pressure)
*2	From Common Rail (High Pressure)
*3	Solenoid
*4	Valve

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory
P1271	Fuel Regulator Circuit Malfunction (EDU Drive)	When either condition below is met (1 trip detection logic): Open or short in pressure discharge valve circuit. There is no valve opening confirmation (IJf) signal from the EDU to the ECM for a specific number of times consecutively, despite the ECM sending valve opening command (PRD) signals after the engine is started	Open or short in pressure discharge valve circuit Pressure discharge valve (built into common rail assembly) Injector driver (EDU)	Comes on	DTC stored
P1272	Fuel Pressure Regulator Malfunction	Pressure discharge valve does not open. 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 (built into common rail assembly) Injector driver (EDU) ECM	Comes on	DTC stored

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Memory

P1271

Fuel Regulator Circuit Malfunction (EDU Drive)

When either condition below is met (1 trip detection logic):

Open or short in pressure discharge valve circuit.
There is no valve opening confirmation (IJf) signal from the EDU to the ECM for a specific number of times consecutively, despite the ECM sending valve opening command (PRD) signals after the engine is started

Open or short in pressure discharge valve circuit
Pressure discharge valve (built into common rail assembly)
Injector driver (EDU)

Comes on

DTC stored

P1272

Fuel Pressure Regulator Malfunction

Pressure discharge valve does not open.

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 (built into common rail assembly)
Injector driver (EDU)
ECM

Comes on

DTC stored

Related Data List
DTC No.	Data List
P1271	Fuel Press Target Common Rail Pressure Pressure Discharge Valve
P1272

Tech Tips

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

After clearing the DTC, drive the vehicle at 50 km/h (31 mph) in third gear, and then decelerate by releasing the accelerator pedal. Check that P1271 is not stored.
P1272:

After clearing the DTC, start and stop the engine twice (wait 30 seconds or more after turning the ignition switch off before starting the engine the second time), and then confirm that P1272 is not stored.

Reference:
Engine Speed	Fuel Pressure (kPa)
Idling	Fuel Press is within +/-5000 kPa of Target Common Rail Pressure
2500 rpm (No engine load)

Results of real-vehicle check:
Condition	Fuel Press (Idling)	Fuel Press (1 Second after Engine Stopped)
Pressure discharge valve normal	35000 kPa	170 kPa
Open in pressure discharge valve circuit	34000 kPa	34300 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 injector driver (EDU) to the ECM, despite the ECM has commanded the injector driver (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 in which a valve is stuck open or closed.

The injector driver (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 injector driver (EDU) interprets this as the IJf signal being low. If this DTC is stored, the ECM enters the fail-safe mode and limits engine power. The fail-safe mode continues until the ignition switch is turned off.

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. In this event, the ECM compares the actual drop rate of the internal fuel pressure and the target drop rate. If the ECM judges that the actual drop rate is smaller than the target, the ECM then judges that the valve is stuck closed and stores 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 stored, the ECM enters fail-safe mode and limits engine power. The fail-safe mode continues until the ignition switch is turned off.

MONITOR STRATEGY

P1271:
Required sensors	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
The vehicle is driven at 50 km/h (31 mph) in 3rd gear, and then decelerated by complete release of the accelerator pedal 3 times.

P1272:
Item	Specification
Item	Minimum	Maximum
Fuel pressure	30000 kPa (306 kgf/cm², 4350 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 injector driver (EDU) for a specific number of times consecutively, despite the ECM sending command signals regularly during deceleration.

P1272:
Specification
The internal pressure stays beyond the specified level after the ignition switch is turned off.

CONFIRMATION DRIVING PATTERN

DTC No.	DTC Detection Drive Pattern
P1271	Ignition switch ON to off and Drive the vehicle at 50 km/h (31 mph) in third gear, and then decelerate by releasing the accelerator pedal
P1272	Ignition switch ON to off

DTC No.

DTC Detection Drive Pattern

P1271

Ignition switch ON to off

and

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

P1272

Ignition switch ON to off

WIRING DIAGRAM


*a	Pressure Discharge Valve
*b	Injector Driver (EDU)

Refer to DTC P0201 Click here.

CAUTION / NOTICE / HINT

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 P062D and P1271 are present simultaneously, there is an open in the INJF wire harness between the injector driver (EDU) and ECM, or there is an open in the wire harness for both an injector and the pressure discharge valve.
Read freeze frame data using the GTS. 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

CHECK IF DTC OUTPUT RECURS

Connect the GTS to the DLC3.
Turn the ignition switch to ON.
Turn the GTS on.
Clear the DTCs.

Powertrain > Engine > Clear DTCs
Turn the ignition switch off for 30 seconds or more.
Turn the ignition switch to ON.
Drive the vehicle at 50 km/h (31 mph) in 3rd gear, and then decelerate by completely releasing the accelerator pedal. Perform this 3 times.
Enter the following menus: Powertrain / Engine / Trouble Codes.

Powertrain > Engine > Trouble Codes

Read the pending DTCs.

Result

Result	Proceed to
DTC P1272 is output	A
DTC P1271 is output	B
DTC P1271 and P1272 are output	B
Other DTCs are output	C

INSPECT PRESSURE DISCHARGE VALVE Click here

GO TO DTC CHART Click here

CHECK COMMON RAIL ASSEMBLY (PRESSURE DISCHARGE VALVE OPERATION)

Inspect the common rail assembly.

Click here

Result

Proceed to
OK
NG

GO TO STEP 14 Click here

GO TO STEP 12 Click here

INSPECT PRESSURE DISCHARGE VALVE

Inspect the pressure discharge valve.

Click here

Result

Proceed to
OK
NG

REPLACE COMMON RAIL ASSEMBLY Click here

CHECK HARNESS AND CONNECTOR (PRESSURE DISCHARGE VALVE - INJECTOR DRIVER (EDU))

Disconnect the pressure discharge valve connector.
Disconnect the injector driver (EDU) connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
B69-1 - B54-1 (RLF+)	Always	Below 1 Ω
B69-2 - B54-2 (RLF-)	Always	Below 1 Ω
B69-1 or B54-1 (RLF+) - Body ground	Always	10 kΩ or higher
B69-2 or B54-2 (RLF-) - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR Click here

CHECK HARNESS AND CONNECTOR (INJECTOR DRIVER (EDU) - ECM)

Disconnect the injector driver (EDU) connector.
Disconnect the ECM connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
B53-5 (PRD) - B76-52 (PRD)	Always	Below 1 Ω
B53-1 (RLF) - B76-123 (RLFF)	Always	Below 1 Ω
B53-5 (PRD) or B76-52 (PRD) - Body ground	Always	10 kΩ or higher
B53-1 (RLF) or B76-123 (RLFF) - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

GO TO STEP 11 Click here

CHECK TERMINAL VOLTAGE (POWER SOURCE OF INJECTOR DRIVER (EDU))

*a
Front view of wire harness connector

(to Injector Driver (EDU))

Disconnect the injector driver (EDU) connectors.
Turn the ignition switch to ON.

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

Standard Voltage

Tester Connection	Condition	Specified Condition
B51-2 (+B) - B51-4 (GND)	Ignition switch ON	11 to 14 V

Result

Proceed to
OK
NG

GO TO INJECTOR CIRCUIT Click here

REPLACE INJECTOR DRIVER (EDU)

Replace the injector driver (EDU).

Click here

Result

Proceed to
NEXT

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

Connect the GTS to the DLC3.
Turn the ignition switch to ON.
Turn the GTS on.
Clear the DTCs.

Powertrain > Engine > Clear DTCs
Turn the ignition switch off for 30 seconds or more.
Turn the ignition switch to ON.
Drive the vehicle at 50 km/h (31 mph) in 3rd gear, and then decelerate by completely releasing the accelerator pedal. Perform this 3 times.
Enter the following menus: Powertrain / Engine / Trouble Codes.

Powertrain > Engine > Trouble Codes

Read the pending DTCs.

Tech Tips

If no pending DTCs are output, proceed to the next step to check "All Readiness".
Perform the following procedure using the GTS to determine whether or not the DTC judgment has been carried out.

Enter the following menus: Powertrain / Engine / Utility / All Readiness.

Powertrain > Engine > Utility

Tester Display

All Readiness
Input DTC P1271 and P1272.

Tester Display
All Readiness

Check the DTC judgment result.

Result

GTS Display	Result	Proceed to
Pending DTC	DTC P1271 and/or P1272 is output	B
All Readiness	NORMAL	A
All Readiness	ABNORMAL	B

Tech Tips

If STATUS is INCOMPLETE or N/A, perform the following procedure 3 times: drive the vehicle at 50 km/h (31 mph) in 3rd gear, and then decelerate by completely releasing the accelerator pedal.

END

REPLACE ECM

Replace the ECM.

Click here

Result

Proceed to
NEXT

GO TO STEP 14 Click here

GO TO INJECTOR CIRCUIT

Go to injector circuit.

Click here

Result

Proceed to
NEXT

GO TO STEP 14 Click here

REPAIR OR REPLACE HARNESS OR CONNECTOR

Repair or replace the harness or connector.

Result

Proceed to
NEXT

GO TO STEP 14 Click here

REPLACE COMMON RAIL ASSEMBLY

Replace the common rail assembly.

Click here

Result

Proceed to
NEXT

BLEED AIR FROM FUEL SYSTEM

Bleed the air from the fuel system.

Click here

Result

Proceed to
NEXT

CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

Connect the GTS to the DLC3.
Turn the ignition switch to ON.
Turn the GTS on.
Clear the DTCs.

Powertrain > Engine > Clear DTCs
Turn the ignition switch off for 30 seconds or more.
Turn the ignition switch to ON.
Drive the vehicle at 50 km/h (31 mph) in 3rd gear, and then decelerate by completely releasing the accelerator pedal. Perform this 3 times.
Enter the following menus: Powertrain / Engine / Trouble Codes.

Powertrain > Engine > Trouble Codes

Confirm that the pending DTC is not output again.

Tech Tips

Perform the following procedure using the GTS to determine whether or not the DTC judgment has been carried out.

Enter the following menus: Powertrain / Engine / Utility / All Readiness.

Powertrain > Engine > Utility

Tester Display

All Readiness
Input DTC P1271 and P1272.
Check the DTC judgment result.

Tech Tips

If STATUS is INCOMPLETE or N/A, perform the following procedure 3 times: drive the vehicle at 50 km/h (31 mph) in 3rd gear, and then decelerate by completely releasing the accelerator pedal.

Result

Proceed to
NEXT

END