CM850 Electronic Control System – FAULT CODE 559 (ISC/QSC/ISL/QSL Automotive, Industrial, or Marine Application)

Injector Metering Rail 1 Pressure – Data Valid but Below Normal Operational Range – Moderately Severe Level


Fault Code: 559
PID: P94
SPN: 94
FMI: 0/18
LAMP: Yellow

Injector Metering Rail 1 Pressure – Data Valid but Below Normal Operational Range – Moderately Severe Level. The ECM has detected that fuel pressure is lower than commanded pressure.

Possibly hard to start, low power, or engine smoke.

Fuel Flow Diagram

Circuit Description

The pressure control loop relies on fuel pressure supplied to the high-pressure pump by the fuel gear pump. The electronic control module (ECM) monitors rail fuel pressure and engine operating conditions and changes the flow command to maintain the proper rail fuel pressure. Changes to the flow command result in opening (or closing) of the fuel pump actuator to supply more (or less) fuel to the high-pressure pump.

The fuel flow circuit includes, in the following order:

  • OEM fuel tank
  • OEM fuel supply line
  • Water stripping fuel filter (10 micron, water stripping, suction side fuel filter)
  • Engine mounted OEM fuel connection
  • Fuel supply tube to ECM cooling plate
  • ECM cooling plate
  • Fuel supply tube to the low-pressure gear pump
  • Fuel supply tube to the pressure-side fuel filter
  • Primary fuel filter (3 micron pressure-side fuel filter)
  • Fuel supply tube to the high-pressure pump
  • High-pressure pump
  • High-pressure system (including fuel rail and fuel rail pressure relief valve), injectors, and high-pressure lines.

Component Location

The high-pressure fuel pump is mounted to the gear housing on the intake side of the engine. Refer to Procedure 100-002 (Engine Diagrams) in Section E for a detailed component location view.

Shop Talk

The troubleshooting steps for Fault Code 559 and Fault Code 2215 are the same.

For all active and non-active Fault Code 559 troubleshooting, reference Fault Code 2215 troubleshooting tree.

Refer to Troubleshooting Fault Code t05-559

Last Modified:  08-Jul-2010