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 assembly 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 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.
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 Assembly (High Pressure)
*3	Solenoid
*4	Valve

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory
P1271	Fuel Regulator Circuit (EDU Drive)	When the condition below is met a certain number of times (0.5 seconds) (1 trip detection logic): Open or short in pressure discharge valve circuit.	Open or short in pressure discharge valve circuit Pressure discharge valve (common rail assembly)	Comes on	DTC stored
P1272	Fuel Pressure Regulator Circuit	The fuel pressure does not decrease while the engine is running (1 trip detection logic).	Open or short in pressure discharge valve circuit (P1271 is stored simultaneously) Pressure discharge valve (common rail assembly) ECM	Comes on	DTC stored

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Memory

P1271

Fuel Regulator Circuit (EDU Drive)

When the condition below is met a certain number of times (0.5 seconds) (1 trip detection logic):

Open or short in pressure discharge valve circuit.

Open or short in pressure discharge valve circuit
Pressure discharge valve (common rail assembly)

Comes on

DTC stored

P1272

Fuel Pressure Regulator Circuit

The fuel pressure does not decrease while the engine is running

(1 trip detection logic).

Open or short in pressure discharge valve circuit (P1271 is stored simultaneously)
Pressure discharge valve (common rail assembly)
ECM

Comes on

DTC stored

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, perform the following procedure 5 times, and then check that P1272 is not output: Drive the vehicle at 50 km/h (31 mph) in third gear, and then decelerate by releasing the accelerator pedal.

Reference
Engine Speed	Common Rail Pressure (kPa)
Idling	Common Rail Pressure is within 5000 kPa of Target Common Rail Pressure
3000 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

CONFIRMATION DRIVING PATTERN

DTC No.	DTC Detection Drive Pattern
P1271	Drive the vehicle at 50 km/h (31 mph) in third gear, and then decelerate by releasing the accelerator pedal
P1272	Drive the vehicle at 50 km/h (31 mph) in third gear, and then decelerate by releasing the accelerator pedal. Perform this 5 times.

MONITOR DESCRIPTION

P1271 (Open or short in pressure discharge valve circuit):
This DTC is output when there is an open or short circuit in the pressure discharge valve circuit. When this DTC is output, the ECM enters fail-safe mode and restricts the engine output. The ECM stays in fail-safe mode until the ignition switch is turned off.

P1272 (Pressure discharge valve stuck closed):
The pressure discharge valve opens when the common rail target fuel pressure decreases during deceleration, decreasing the fuel pressure in the common rail assembly. The ECM compares the speed that the fuel pressure decreases with the speed that the common rail target fuel pressure decreases.

When the ECM determines that the decreasing rate of the fuel pressure is smaller than the common rail target fuel pressure, the ECM determines that the valve is stuck closed or there is an injection or supply pump assembly malfunction (overpressure) and outputs this DTC.

When this DTC is output, the ECM enters fail-safe mode and restricts the engine output. The ECM stays in fail-safe mode until the ignition switch is turned off.

WIRING DIAGRAM


*a	PLV
*b	Pressure Discharge Valve

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 do not recur.
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.

Powertrain > Engine and ECT > 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 5 times.
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Read the pending DTCs.

Powertrain > Engine and ECT > Trouble Codes

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)

Connect the GTS to the DLC3.
Turn the ignition switch to ON and turn the GTS on.
Enter the following menus: Powertrain /Engine / Utility / Pressure Discharge Valve Check.

Click here

Powertrain > Engine and ECT > Utility

Tester Display

Pressure Discharge Valve Check
Select "Close to Open Check".

Tester Display
Pressure Discharge Valve Check

Read the value of "Open and Engine OFF".

OK
0.5 MPa or less

Tech Tips

When the system is normal, the value of "Open and Engine OFF" should be at or close to 0 MPa.
When the fuel pressure value of "Open and Engine OFF" does not become equal to or less than 0.5 MPa, the pressure discharge valve may be stuck closed.
When the fuel pressure values of "Close and Engine OFF" and "Open and Engine OFF" are both 0 MPa, the pressure discharge valve may be stuck open or there may be a fuel leak.
Perform "Always Closed Check" if the value is not 0 MPa when the pressure discharge valve is open during "Close to Open Check". If the results are the same as during "Close to Open Check", there is a pressure discharge valve operation malfunction.

Result

Proceed to
OK
NG

GO TO STEP 5 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.
Clear the DTCs.

Powertrain > Engine and ECT > 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 releasing the accelerator pedal. Perform this 5 times.
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Powertrain > Engine and ECT > Trouble Codes

Confirm that the 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 and ECT / Utility / All Readiness.

Powertrain > Engine and ECT > Utility

Tester Display

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

Tech Tips

Check that STATUS is NORMAL. If STATUS is INCOMPLETE or N/A, perform the following procedure 5 times: drive the vehicle at 50 km/h (31 mph) in 3rd gear, and then decelerate by completely releasing the accelerator pedal.

Tester Display
All Readiness

Result

Result	Proceed to
P1272 is output	A
No DTC is output	B

END

REPLACE FUEL SUPPLY PUMP ASSEMBLY

Replace the fuel supply pump 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

CHECK DTC OUTPUT

Connect the GTS to the DLC3.
Turn the ignition switch to ON and turn the GTS on.
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Read the DTCs.

Powertrain > Engine > Trouble Codes

Result

Proceed to
NEXT

END

INSPECT COMMON RAIL ASSEMBLY (PRESSURE DISCHARGE VALVE RESISTANCE)

Inspect the common rail assembly.

Click here

Result

Proceed to
OK
NG

GO TO STEP 3 Click here

CHECK HARNESS AND CONNECTOR (PRESSURE DISCHARGE VALVE - ECM)

Disconnect the pressure discharge valve connector.
Disconnect the ECM connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
Z3-2 (COM3) - C58-2 (PRV+)	Always	Below 1 Ω
Z3-1 (PLV) - C58-1 (PRV-)	Always	Below 1 Ω
Z3-2 (COM3) or C58-2 (PRV+) - Body ground and other terminals	Always	10 kΩ or higher
Z3-1 (PLV) or C58-1 (PRV-) - Body ground and other terminals	Always	10 kΩ or higher

Reconnect the pressure discharge valve connector.

Reconnect the ECM connector.

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR Click here

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

Connect the GTS to the DLC3.
Clear the DTCs.

Powertrain > Engine and ECT > 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 5 times.
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Read the pending DTCs.

Powertrain > Engine and ECT > Trouble Codes

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.

Powertrain > Engine and ECT > 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	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 5 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 5 Click here

REPAIR OR REPLACE HARNESS OR CONNECTOR

Repair or replace the harness or connector.

Result

Proceed to
NEXT

GO TO STEP 5 Click here