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 of which are internal to the fuel supply pump. This high pressure is regulated by the engine control module (ECM) using the fuel rail pressure (FRP) regulator dependant upon values from the FRP sensor attached to the fuel rail.

If the ECM detects that the fuel pressure is a certain pressure lower than the desired fuel rail pressure for a certain length of time, this DTC will set.

Condition for Running the DTC
- DTCs P0089, P0091, P0092, P0192, P0193, P0335, P0336, P0602, P0642 and P0643 are not set.
- The battery voltage is between 10-16 volts.
- The barometric pressure (BARO) is more than 11 psi (75 kPa).
- The fuel rail pressure (FRP) regulator commanded fuel flow is more than a threshold.

Condition for Setting the DTC
- The ECM detects that the actual fuel rail pressure is less than desired pressure by 4350 psi (30 MPa) for longer than 10 seconds.

Action Taken When the DTC Sets
- The ECM illuminates the malfunction indicator lamp (MIL) on the second consecutive driving cycle 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 Freeze Frame/Failure Records on the second consecutive driving cycle when the diagnostic runs and fails
- The ECM inhibits cruise control.
- The ECM inhibits PTO control.

Condition for Clearing the MIL/DTC
- The ECM turns OFF the MIL after 3 consecutive driving cycles when the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes after the key is cycled.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic after the ECM turns OFF the MIL.
- Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
- An intermittently sticking fuel rail pressure (FRP) regulator may have allowed the fuel pressure to drop.
- Normal Actual Fuel Rail Pressure readings on the scan with the engine running in Park or Neutral at idle are around 3650 to 5050 psi (25 to 35 MPa) and around 14500 to 21750 psi (100 to 150 MPa) in Park or Neutral at W.O.T. (accelerator pedal full travel).
- An intermittently sticking fuel injector may have allowed the fuel pressure to drop too much. Use a scan tool to perform the Cylinder Power Balance test for each injector. Verify a consistent engine speed change when commanding each fuel injector ON and OFF.
- A skewed FRP sensor value (shifted to a lower pressure) can set this DTC. The Actual Fuel Rail Pressure on the scan tool should read 0 psi (0 MPa) with the key ON and engine OFF after the engine has stopped running for a minimum of 2 minutes.
- Resistance in the FRP sensor low reference circuit can set this DTC. Ensure that the sensor low reference circuit has no resistance and the connectors are tight and free of corrosion.

NOTE:
- This DTC most likely indicates a loss of fuel pressure by a restricted suction side fuel line. Inspect the suction side fuel restriction between the fuel supply pump and fuel tank.
- The Actual Fuel Rail Pressure on scan tool will only update with the engine running or one time after the key is cycled when the ignition has been turned OFF for longer than 10 seconds.
- 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.
- If the fuel tank is empty or near empty, air might be allowed to go into the fuel system. With air in the fuel system, smooth flow of fuel into the supply pump is interrupted and this DTC may set. Perform bleeding of fuel system after refilling.


Test Description
The number below refers to the step number on the diagnostic table.
5. This step checks for a fuel restriction by determining if a high vacuum is being pulled on the fuel system during normal operation.
6. This step checks for an air leak on the suction side of the fuel system by determining if a vacuum can be pulled when a fuel line is plugged.

DTC P1093
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Engine Control Module (ECM) Connector End Views

Step 4:

Step 5 - 6:

Step 7 - 10:

Step 11 - 16:

Step 17 - 18: