P1085

DTC P1085 High Pressure Fuel Pump Performance

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 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 went excessively high for a certain length of time this DTC will set. If this DTC is set the fuel pressure was too high and the pressure limiter valve did not active or did not active quick enough.

Condition for Running the DTC

^ DTCs P0089 P0091 P0092 P0192 P0193 P0642 and P0643 are not set.
^ The ignition switch is ON.
^ The engine is running.

Condition for Setting the DTC

Either of the following condition is met:
^ The ECM detects that the actual fuel rail pressure is more than 28,600psi (197 MPa) for longer than 35 seconds.
^ The ECM detects that the actual fuel rail pressure is more than 33,400 psi (230 MPa) for longer than 1 second.

Action Taken When the DTC Sets

^ The ECM will not illuminate the MIL or SVS lamp. Refer to DTC Type Definitions for Action Taken When the DTC Sets - Type D.

Condition for Clearing the DTC

^ Refer to DTC Type Definitions for Condition for Clearing the DTC - Type D.

Diagnostic Aids

^ An intermittently sticking FRP regulator may have allowed the fuel pressure to become high enough to set this DTC.
^ Normal Actual Fuel Rail Pressure readings on the scan tool with the engine running in neutral at idle is around 3900 to 4800 psi (27 to 33 MPa) after warm up.
^ A skewed FRP sensor value can set this DTC. The FRP Sensor on the scan tool should read 0.9 to 1.0 volt after the engine has stopped running for a minimum of 30 seconds.

Test Description

The numbers below refers to the step number on the Circuit! System Testing.

7. This step checks for a fuel restriction by determining if a high vacuum is being pulled on the fuel system during normal operation.

8. 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.

Circuit/System Testing DTC P1085