Lexus IS250 IS220d GSE20 ALE20 2AD-FHV ENGINE CONTROL SYSTEM
TYPICAL MALFUNCTION THRESHOLDS
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)
CHECK IF DTC OUTPUT RECURS (SEE IF DTC IS OUTPUT AGAIN)
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:
| 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 engine 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 |
- HINT:
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.
After clearing the DTC, start and stop the engine twice, and then confirm that P1272 is not present.
| Engine Speed | Fuel Pressure (MPa) |
| Idling | Approximately 37 to 43 |
| 2,500 rpm (No engine load) | Approximately 60 to 66 |
MONITOR DESCRIPTION
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.
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
| Required sensors | EDU |
| Frequency of operation | Continuous |
| Duration | 3 seconds |
| CHK ENG operation | 1 driving cycle |
| Required sensors | Fuel pressure sensor |
| Frequency of operation | Once per driving cycle |
| Duration | 1 second |
| CHK ENG operation | 2 driving cycles |
TYPICAL ENABLING CONDITIONS
| Specification |
| Drive the vehicle at 50 km/h (31 mph) in 3rd gear and then decelerate by completely releasing the accelerator pedal |
| 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
| Specification |
| There is no confirmation signals from the EDU, despite the ECM sending the command signals regularly during deceleration |
| Specification |
| The internal pressure stays beyond the specified level after the engine switch was turned OFF |
WIRING DIAGRAM
INSPECTION PROCEDURE
- NOTICE:
- After replacing the ECM, the new ECM needs registration and initialization .
- HINT:
| 1.READ DTC OUTPUT |
Connect the intelligent tester to the DLC3.
Turn the engine switch ON (IG) and turn the intelligent tester ON.
Enter the following menus: "Powertrain / Engine / DTC".
Read DTCs.
- Result:
Display (DTC output) Proceed to P1271 or P1271 and P1272 A P1272 B
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| A | |
| 2.INSPECT COMMON RAIL ASSEMBLY (PRESSURE DISCHARGE VALVE) |
Disconnect the E68 pressure discharge valve connector.
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
Reconnect the pressure discharge valve connector.
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| OK | |
| 3.CHECK HARNESS AND CONNECTOR (PRESSURE DISCHARGE VALVE - EDU) |
Disconnect the E84 EDU connector.
Disconnect the E68 pressure discharge valve connector.
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
Reconnect the EDU connector.
Reconnect the pressure discharge valve connector.
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| OK | |
| 4.CHECK HARNESS AND CONNECTOR (ECM - EDU) |
Disconnect the E85 EDU connector.
Disconnect the E59 ECM connector.
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
Reconnect the EDU connector.
Reconnect the ECM connector.
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| OK | |
| 5.INSPECT EDU (POWER SOURCE CIRCUIT) |
Disconnect the E86 EDU connector.
Turn the engine switch ON (IG).
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
Reconnect the EDU connector.
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| OK | |
| 6.REPLACE EDU |
| NEXT | |
| 7.CHECK IF DTC OUTPUT RECURS (SEE IF DTC IS OUTPUT AGAIN) |
Connect the intelligent tester to the DLC3.
Turn the engine switch ON (IG) and turn the tester ON.
Clear DTCs.
Start the engine.
Enter the following menus: Powertrain / Engine / DTC.
Read the DTCs using the intelligent tester.
- Result:
Display (DTC output) Proceed to P1271 and/or P1272 A No output B
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| A | ||
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| 8.REPLACE COMMON RAIL ASSEMBLY |
| NEXT | ||
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