P1093

DTC P1093

Description
The common rail fuel system is comprised of two fuel pressure sections: a suction side between the fuel tank and the fuel supply pump and a high-pressure side between the fuel supply pump and the fuel injectors. Fuel is drawn from the fuel tank via a feed pump and then pumped into the fuel rail by two plungers, all which are internal to the fuel supply pump. This high pressure is regulated by the engine control module (ECM) using the suction control valve (SCV) dependant upon values from the fuel rail pressure (FRP) sensor attached to the fuel rail.

Under normal conditions, the fuel pressure will oscillate slightly due to the characteristics of the two-plunger fuel supply pump system. However, if one of the plungers is stuck or the cylinder it rides in is worn out, fuel pressure oscillations will be much higher. If the ECM detects that the fuel pressure is oscillating too much continuously for a certain length of time, this DTC will set.

Condition for Running the DTC
- The ignition switch is ON.
- Deviation of rail pressure is less than 290 psi (2 MPa).
- Deviation of commanded fuel feed quantity is less than 2 mm3/stroke.
- The engine speed and engine load are stable.

Condition for Setting the DTC
- The ECM detects that the oscillation of fuel feed quantity is more than threshold.
- Oscillations have occurred continuously for 1000 times (2 tests per crankshaft revolution).

Action Taken When the DTC Sets
- The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.
- The ECM limits the fuel injection quantity within 50%.
- The ECM limits the fuel rail pressure within 11600 psi (80 MPa).
- The ECM closes the EGR valve and holds to close position.
- The ECM inhibits cruise control.
- The ECM inhibits PTO control.

Condition for Clearing the DTC
- A current DTC clears when the ignition is turned OFF.
- Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
- Make sure the fuel pressure sensor wiring is not interfering with the crankshaft position (CKP) or camshaft position (CMP) sensor wiring.

NOTE: The fuel system from the fuel tank(s) to the fuel supply pump is under a slight vacuum with the engine running. As a result, air can enter the fuel system if these connections are not tight or if there is a crack in one of the fuel hoses. Air in the fuel system will cause fuel rail pressure fluctuations especially at high engine speed and load, which may set this DTC.

DTC P1093

Schematic Reference: Engine Controls Schematics

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