P1093

DTC P1093

CIRCUIT DESCRIPTION
The engine control module (ECM) uses the fuel rail pressure (FRP) sensor to determine fuel pressure to the fuel injectors. This is then compared to the calculated target fuel pressure as determined by the ECM. The ECM adjusts the FRP by modulating the duty cycle of the control driver of the fuel pressure regulator. Injector pulse duration is determined by the measured rail pressure and the target injection fuel into each cylinder. If a sensor circuit malfunction is detected, or the commanded fuel injection pump flow is not within the proper range for a given engine load and speed, DTCs will be set.

CONDITIONS FOR RUNNING THE DTC
- DTCs P0192, P0193, or P0641 are not set.
- The ignition is ON.

CONDITIONS FOR SETTING THE DTC
The difference between commanded fuel pressure and actual fuel pressure is more than 20 MPa.

or

The FRP regulator fuel flow is more than 15,000 mm(3) at 800 RPM, or more than 38,000 mm(3) at 2,000 RPM.

ACTION TAKEN WHEN THE DTC SETS (CALIFORNIA)
- The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails-The control module stores this information in the Freeze Frame/Failure Records.

ACTION TAKEN WHEN THE DTC SETS (FEDERAL)
- The control module stores the DTC information into memory when the diagnostic runs and fails.
- The MIL will not illuminate.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
- The driver information center, if equipped, may display a message.

CONDITIONS FOR CLEARING THE MIL/DTC (CALIFORNIA)
- The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Use a scan tool in order to clear the MIL and the DTC.

CONDITIONS FOR CLEARING THE DTC (FEDERAL)
- A current DTC Last Test Failed clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Use a scan tool in order to clear the DTC.

DIAGNOSTIC AIDS
- This DTC does not set for an idle condition.
- A number of conditions may cause DTC P0087 and DTC P1093 to set:
- Excessive fuel return to the tank
- A fuel injection pump failure
- A fuel pressure regulator (RPCV) failure
- If you have to prime the fuel system, check for the following conditions:
- A restricted fuel supply line
- A fuel supply line air leak. Refer to Fuel System Diagnosis (Pickup) Fuel System Diagnosis (Cab Chassis). Component Tests and General Diagnostics
- A sticking fuel pressure regulator may set this DTC. Refer to Fuel System Diagnosis - High Pressure Side. Perform this test under the conditions for which the DTC set. Component Tests and General Diagnostics
- If the problem is still intermittent, refer to Intermittent Conditions. Diagnostic Strategies

TEST DESCRIPTION

Steps 1-4:

Steps 5-8:

Steps 9-12:

Steps 13-19:

The numbers below refer to the step numbers on the diagnostic table.
2. If the fuel temperature is high enough to set DTC P0168, the fuel may be thin enough to cause this DTC to set.
4. The engine will not start if the fuel leak is large enough.
5. This step checks for an inaccurate fuel rail pressure sensor.
6. This step checks for fuel leaks into the engine oil.
7. This step checks for a restriction in the fuel system between the fuel injection pump and the fuel tank.
8. This test checks to see if the fuel injection pump is able to supply maximum fuel pressure at idle. The fuel injection pump should be able to create 145-158 MPa at idle. At higher ambient temperatures, the fuel pressure will be lower, but still more than 145 MPa.
9. This step checks for a restriction in the fuel system between the fuel injection pump and the fuel tank that may only cause symptoms at higher engine speed and load conditions.
11. This step checks to see if the fuel rail pressure sensor wiring and ECM are functioning normally.
13. If the vacuum is still too high in the fuel supply system after replacing the fuel filter, there is a restriction in the fuel supply lines or sending unit in the fuel tank.