Cummins ISB CM850 (2003-06) Fault Code: 2311 PID: SID 81 SPN: 633 FMI: 11 Fueling Actuator Number 1 Circuit Error Conditions Exists. Fuel pump actuator circuit resistance too high or too low.

Cummins ISB CM850 (2003-06) Fault Code: 2311 PID: SID 81 SPN: 633 FMI: 11 Fueling Actuator Number 1 Circuit Error Conditions Exists. Fuel pump actuator circuit resistance too high or too low.

If this fault code occurs during road test or sea trial, verify that all connectors are clean and free of corrosion before replacing components. This fault code can become active for any of the following reasons:

1)Fuel pump actuator high resistance
2)Engine harness high resistance
3)Loose, worn, or corroded connectors or pins
4)Fuel pump actuator with low internal resistance
5)Fuel pump actuator or engine harness that has shorted to ground
6)Intermittent circuit failures that cause the fuel pressure to exceed the fuel rail pressure relief valve opening pressure.

If an intermittent electrical circuit problem of the fuel pump actuator circuit exists, it is possible for the fault code to become active then inactive during normal engine operation. For example, if a poor connection causes an intermittent open or short circuit, the normally open valve will open in a fraction of a second while the circuit is faulty causing the fuel rail pressure relief valve to open. Following the event that caused the fuel rail pressure relief valve to open, the ECM will attempt to reset the fuel rail pressure relief valve, provided the fuel pump actuator circuit is not still failed.

Following any event that opens the fuel rail pressure relief valve, the fuel rail pressure relief valve will regulate the fuel pressure at approximately 90 mPa [13053 psi]. If the ECM is still capable of controlling fuel pressure, the following will occur:

1)The measured fuel pressure will reduce to 60 mPa [8702.3 psi] as the ECM prepares to re-seat the fuel rail pressure relief valve.
2)Once pressure is 60 mPa [8702.3 psi] and engine speed is greater than 1200 rpm, the ECM will momentarily close the fuel pump actuator. This action will reduce the fuel rail pressure (to less than 2 mPa [290 psi] for a fraction of a second) so that the fuel rail pressure relief valve will reset. At light engine loads, especially if the engine is sped while the driveline is not engaged, engine power interruption will be noticeable while the ECM attempts to reset the fuel rail pressure relief valve.
3)Once the ECM detects that the fuel rail pressure relief valve is reset, normal engine operation will resume and Fault Code 2311 will become inactive.

Possible repairs:

1)Replace the fuel pump actuator.
2)Replace the faulty electronic fuel control actuator.
3)Repair or replace the engine harness.