ECD SYSTEM (w/ DPF), Diagnostic DTC:P1271, P1272

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

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, refer to System Description Click here.
For more information on the injector driver, refer to System Description Click here.
If P1271 and/or P1272 is present, refer to the DTC chart for the fuel system Click here.

P1271
DTC Detection Drive Pattern	DTC Detection Condition	Trouble Area
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	When either condition below is met a certain number of times (0.5 seconds) (1 trip detection logic): Open or short in pressure discharge valve circuit. There is no valve opening confirmation (RLF) signal from the injector driver 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 (common rail assembly) Injector driver

P1272
DTC Detection Drive Pattern	DTC Detection Condition	Trouble Area
Ignition switch ON to OFF	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 stored simultaneously) Pressure discharge valve (common rail assembly) Injector driver ECM

Related Data List
DTC No.	Data List
P1271	Common Rail Pressure 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 by entering the following menus:

Powertrain / Engine and ECT / Data List / Common Rail Pressure.
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 output.
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	Common Rail Pressure is within 5000 kPa of Target Common Rail Pressure
2500 rpm (No engine load)

Results of Real-vehicle Check
Condition	Common Rail Pressure (Idling)	Common Rail Pressure (1 Second after Engine Stopped)
Pressure discharge valve normal	35000 kPa	500 kPa
Open in pressure discharge valve circuit	35000 kPa	30000 kPa

MONITOR DESCRIPTION

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

This DTC will be stored if there is no valve opening confirmation (RLF) signal sent from the injector driver to the ECM despite the ECM commanding the injector driver 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 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 interprets this as the RLF signal being low. If this DTC is stored, the ECM enters fail-safe mode and limits engine power. The ECM continues operating in fail-safe mode until the ignition switch is turned off.

P1272 (Pressure discharge valve stuck closed):

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 determines 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 ECM continues operating in fail-safe mode until the ignition switch is turned off.

MONITOR STRATEGY

P1271
Required sensors	Injector driver
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 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.

WIRING DIAGRAM

Refer to DTC P0201 Click here.

INSPECTION PROCEDURE

Note

Inspect the fuses of circuits related to this system before performing the following inspection procedure.
After replacing the ECM, the new ECM needs registration Click here and initialization Click here.
After replacing the fuel supply pump assembly, the ECM needs initialization Click here.
After replacing an injector assembly, the ECM needs registration 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 and ECM, or there is an open in the wire harness for both an injector assembly 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.
Clear the DTCs Click here.
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 and ECT / Trouble Codes.

Read the pending DTCs.

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

INSPECT COMMON RAIL ASSEMBLY (PRESSURE DISCHARGE VALVE RESISTANCE) Click here

GO TO DTC CHART Click here

CHECK COMMON RAIL ASSEMBLY (PRESSURE DISCHARGE VALVE OPERATION)
1. Check the common rail assembly Click here.
OK
CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

NG
REPLACE COMMON RAIL ASSEMBLY Click here
INSPECT COMMON RAIL ASSEMBLY (PRESSURE DISCHARGE VALVE RESISTANCE)
1. Inspect the common rail assembly Click here.
NG
REPLACE COMMON RAIL ASSEMBLY Click here

OK

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

Disconnect the injector driver connector.
Disconnect the pressure discharge valve connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
D87-2 - B63-1 (RLF+)	Always	Below 1 Ω
D87-1 - B63-2 (RLF-)	Always	Below 1 Ω
D87-2 or B63-1 (RLF+) - Body ground	Always	10 kΩ or higher
D87-1 or B63-2 (RLF-) - Body ground	Always	10 kΩ or higher

Reconnect the injector driver connector.
Reconnect the pressure discharge valve connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR Click here

CHECK HARNESS AND CONNECTOR (ECM - INJECTOR DRIVER)

Disconnect the injector driver connector.
Disconnect the ECM connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
B62-5 (PRD) - D99-52 (PRD)	Always	Below 1 Ω
B62-8 (INJF) - D99-51 (INJF)	Always	Below 1 Ω
B62-5 (PRD) or D99-52 (PRD) - Body ground	Always	10 kΩ or higher
B62-8 (INJF) or D99-51 (INJF) - Body ground	Always	10 kΩ or higher

Reconnect the injector driver connector.
Reconnect the ECM connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR Click here

INSPECT INJECTOR DRIVER (POWER SOURCE CIRCUIT)

Text in Illustration

*a
Front view of wire harness connector

(to Injector Driver)

Disconnect the injector driver connectors.

Text in Illustration
*a	Front view of wire harness connector (to Injector Driver)

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

Standard Voltage

Tester Connection	Switch Condition	Specified Condition
B60-2 (+B) - B60-4 (GND)	Ignition switch ON	11 to 14 V

Reconnect the injector driver connector.

GO TO INJECTOR CIRCUIT Click here

REPLACE INJECTOR DRIVER
1. Replace the injector driver Click here.
NEXT

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

Connect the GTS to the DLC3.
Clear the DTCs Click here.
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 and ECT / 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 and ECT / Utility / All Readiness.
Input DTC P1271 and P1272.

Check the DTC judgment result.

Result
GTS Display	Result	Proceed to
Pending 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.

REPLACE ECM Click here

END

REPAIR OR REPLACE HARNESS OR CONNECTOR
1. Repair or replace the harness or connector.
NEXT
CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here
GO TO INJECTOR CIRCUIT
1. Go to injector circuit Click here.
NEXT
CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here
REPLACE ECM
1. Replace the ECM Click here.
NEXT
CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here
REPLACE COMMON RAIL ASSEMBLY
1. Replace the common rail assembly Click here.
NEXT
BLEED AIR FROM FUEL SYSTEM
1. Bleed the air from the fuel system Click here.
NEXT
CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED
1. Connect the GTS to the DLC3.
2. Clear the DTCs Click here.
3. Turn the ignition switch off for 30 seconds or more.
4. Turn the ignition switch to ON.
5. 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.
6. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
7. 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.
  1. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
  2. Input DTC P1271 and P1272.
  3. 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.
NEXT

END