P0087

DTC P0087

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 suction control valve (SCV) dependant upon values from the fuel rail pressure (FRP) sensor attached to the fuel rail. In case of fuel rail overpressure, a pressure limiter valve threaded into the fuel rail will open to release overpressure and return fuel back to the fuel tank.

If the ECM detects that the fuel pressure went excessively high, then sharply decreased, this DTC will set indicating high fuel pressure, which activated the pressure limiter valve.

Condition for Running the DTC
- The battery voltage is between 10-16 volts.
- The ignition switch is ON.

Condition for Setting the DTC
- When the pressure limiter valve is activated with over pressure (more than 27560 psi [190 MPa]) in the fuel rail.

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 time the diagnostic fails. The ECM stores information in the Failure Records.
- The ECM limits accelerator control range within 55%.
- 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
- An intermittently sticking suction control valve (SCV) may have allowed the fuel pressure to become high enough to open the pressure limiter valve.
- 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).
- A shorted SCV or a short between the high and low control circuit will set P0087 and may not set an electrical P0091 or P0092 DTC.
- 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 fuel rail pressure (FRP) sensor value (shifted to a higher 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.

NOTE:
- 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.

Test Description
The numbers below refer to the step number on the diagnostic table.
6. This step checks for a fuel restriction by determining if a high vacuum is being pulled on the fuel system during normal operation.
7. 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 P0087

Schematic Reference: Engine Controls Schematics

Step 6 - 8:

Step 9 - 11:

Step 12 - 18: