GSIC - Global Service Information Center

### DTC P0088/78 Fuel Rail / System Pressure - Too High

### DTC P1229/78 Fuel Pump System

## for Preparation Click here

## DESCRIPTION

HINT:

1. For more information on the supply pump (suction control valve) and common rail system, refer to the system description (Click here).
2. If P0088/78 and/or P1229/78 is present, refer to the "Diagnostic Trouble Code (DTC) Table for Common Rail System" (Click here).

Refer to the system description (Click here).

DTC No. | DTC Detection Condition | Trouble Area

P0088/78

Internal fuel pressure of common rail is too high:
Fuel pressure exceeds 200 MPa (2,039 kgf/cm2, 29,007 psi)
(1 trip detection logic)

1. Supply pump (suction control valve)
2. Pressure limiter
3. Short in supply pump (suction control valve) circuit
4. ECM

P1229/78

Fuel over-feed:
Internal fuel pressure continues exceeding target fuel pressure despite ECM closing suction control valve
(1 trip detection logic)

1. Short in supply pump (suction control valve) circuit
2. Supply pump (suction control valve)
3. ECM

HINT:

  When DTC P0088/78 and/or P1229/78 is set, check the internal fuel pressure of the common rail by entering the following menus on the intelligent tester: Powertrain / Engine / Data List / Fuel Press.

Reference:

  Engine Speed | Fuel Pressure
  Idling | Approximately 30 to 40 MPa
  3,000 rpm (No engine load) | Approximately 50 to 70 MPa

## MONITOR DESCRIPTION

P0088/78 (Internal fuel pressure too high):

1. The ECM sets this DTC if the fuel pressure inside the common rail is beyond 200 MPa (2,039 kgf/cm2, 29,007 psi). This DTC indicates that: 1) the suction control valve may be stuck open, 2) there may be an open or short in the suction control valve circuit.
   If this DTC is set, the ECM enters fail-safe mode and limits the engine power. The fail-safe mode continues until the ignition switch is turned OFF.

P1229/78 (Fuel over-feed):

1. The ECM sets this DTC if the actual fuel pressure inside the common rail remains higher than the target fuel pressure, despite the ECM closing the suction control valve. This DTC indicates that the suction control valve may be stuck open, or there may be a short in its circuit. Under this condition, the pressure discharge valve operates frequently.
   If this DTC is set, the ECM enters fail-safe mode and limits engine power. The fail-safe mode continues until the ignition switch is turned OFF.

## MONITOR STRATEGY

P0088/78:
Required sensors | Fuel pressure sensor
Frequency of operation | Continuous
Duration | 1 second
MIL operation | 1 driving cycle

P1229/78:
Required sensors | Fuel pressure sensor
Frequency of operation | Continuous
Duration | 1 minute
MIL operation | 1 driving cycle

## TYPICAL ENABLING CONDITIONS

P0088/78:
Specification
The monitor will not run if the fuel pressure sensor or suction control valve circuit is malfunctioning

P1229/78:
Item | Specification
Target fuel pressure variation | Small
The monitor will not run if the fuel pressure sensor or suction control valve circuit is malfunctioning

## TYPICAL MALFUNCTION THRESHOLDS

P0088/78:
Detection Criteria | Threshold
Fuel pressure sensor | 200 MPa (2,039 kgf/cm2, 29,007 psi) or more

P1229/78:
Detection Criteria | Threshold
The internal fuel pressure of the common rail when the suction control valve is closed | Remains higher than target fuel pressure

## WIRING DIAGRAM

## INSPECTION PROCEDURE

HINT:

  Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, and other data from the time the malfunction occurred.

NOTICE:

  If the ECM is replaced, the new ECM needs initialization (Click here).

1.CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0088/78 AND/OR P1229/78)

1. Connect the intelligent tester to the DLC3.

1. Turn the ignition switch ON and turn the intelligent tester ON.

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

1. Read the DTCs.

   Result:

     Display (DTC Output) | Proceed to
     P0088/78, or P0088/78 and P1229/78 | A
     P1229/78 | B
     P0190/49, P0192/49 and/or P0193/49 | C

| B |

Go to step 3

| C |

GO TO RELEVANT DTC CHART

A |

2.REPLACE COMMON RAIL ASSEMBLY (PRESSURE LIMITER)

HINT:

  After clearing the DTC(s), drive the vehicle at 50 km/h (31 mph) for 5 minutes, and then confirm that P0088/78 and/or P1229/78 is not present again.

NEXT |

3.INSPECT SUPPLY PUMP ASSEMBLY (SUCTION CONTROL VALVE)

1. Disconnect the S8 valve connector.

1. Measure the resistance of the suction control valve.

   Standard resistance:
     1.9 to 2.3 Ω at 20°C (68°F)

| NG |

REPLACE SUPPLY PUMP ASSEMBLY (SUCTION CONTROL VALVE)

OK |

4.CHECK IF DTC OUTPUT RECURS (DTC P1229/78)

1. Connect the intelligent tester to the DLC3.

1. Turn the ignition switch ON and turn the intelligent tester ON.

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

1. Clear the DTC(s).

1. Disconnect the suction control valve connector and then start the engine. Wait for 1 minute.

   HINT:
     If the engine does not start, the suction control valve is normal. Check the ECM (see "CHECK ECM (PCV SIGNAL)" procedures below).

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

1. Read the DTCs.

   Result:

     Display (DTC Output) | Proceed to
     No output | A
     P1229/78 | B

| B |

REPLACE SUPPLY PUMP ASSEMBLY (SUCTION CONTROL VALVE)

A |

5.CHECK WIRE HARNESS (SUCTION CONTROL VALVE - ECM)

1. Disconnect the S8 valve connector.

1. Disconnect the E8 ECM connector.

1. Measure the resistance of the wire harness side connectors.

   Standard resistance:

     Tester Connection | Specified Condition
     S8-1 (PCV+) - E8-2 (PCV+) | Below 1 Ω
     S8-2 (PCV-) - E8-1 (PCV-) | Below 1 Ω
     S8-1 (PCV+) or E8-2 (PCV+) - Body ground | 10 kΩ higher
     S8-2 (PCV-) or E8-1 (PCV-) - Body ground | 10 kΩ higher

| NG |

REPAIR OR REPLACE HARNESS AND CONNECTOR

OK |

6.CHECK ECM (PCV SIGNAL)

1. While cranking or idling the engine, check the waveform of the ECM connector using an oscilloscope.

   Standard:

     Tester Connection | Specified Condition
     E8-2 (PCV+) - E8-1 (PCV-) | Correct waveform shown

   Tool Setting | Condition
   10 V/DIV., 5 msec./DIV. | Idling or cranking with warm engine

HINT:

1. The waveform varies depending on the suction control valve operation.
2. After clearing the DTC(s), drive the vehicle at 50 km/h (31 mph) for 5 minutes, and then confirm that P0088/78 or P1229/78 is not output again.

| NG |

REPLACE ECM

OK |

CHECK IF DTC OUTPUT RECURS (DTC P0088/78 OR P1229/78)