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, 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.

The ECM detects that the actual fuel rail pressure is less than the desired pressure by 30 MPa for longer than 10 seconds.

DTC P1093 is a Type B DTC.

DTC P1093 is a Type B DTC.

Inspect for any recent engine mechanical repairs. An incorrectly installed fuel rail pressure (FRP) regulator will cause this DTC to set.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Special Tools Required

Verify the integrity of the Fuel system, fuel rail pressure (FRP) regulator by inspecting for the following conditions:

Important: You must perform Circuit/System Verification before proceeding with Circuit/System Testing.

1. Start the engine and operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
2. Observe the Actual Fuel Pressure parameter with a scan tool. The actual pressure should be 0 MPa with the engine not running at operating temperature.

⇒	If the pressure difference between the actual and desired pressure are more than 2 MPa, replace the fuel rail pressure sensor.

3. Observe the Actual Fuel Pressure parameter with a scan tool. The actual pressure should be 30 MPa with the engine idling at operating temperature.
4. Change the fuel pressure with a scan tool, incrementing through the entire fuel pressure range. The fuel pressure should increment and stabilize through the entire fuel pressure range with the actual desired fuel pressure within 2 MPa of each other.

⇒	If the pressure difference between the actual and desired pressure are more than 2 MPa, replace the fuel pressure regulator.

5. Observe the Actual Fuel Pressure parameter with a scan tool. The actual pressure should be 197 MPa with the wide open throttle (WOT) at operating temperature.

⇒	If the pressure ever exceeds the specified value, replace the FRP sensor.

6. Connect the suction side of the EN-47667 with the J 44638 assembly in series with the filter housing and the disconnected fuel hose. Bleed the fuel system by priming the priming pump until it becomes firm, then crank over the engine for a maximum of 5 seconds. Repeat as necessary until the engine starts.
7. Let the engine run at idle for at least 1 minute. Monitor the fuel vacuum/pressure gage while holding the engine speed higher than 2,500 RPM for a minimum of 1 minute.
8. Observe the fuel vacuum/pressure with a pressure gage. The vacuum/pressure gage ever indicate a larger vacuum than 5 in Hg.

⇒	If vacuum/pressure gage ever indicate a larger vacuum than the specified amount during the test, repair or replace the fuel line/fuel filter/fuel tank.

9. Test the injector for injector balance test with a scan tool.

⇒	If engine noise does not change, replace the fuel injector.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.