Cummins ISB CM850 (2003-06) Fault Code: 559 (ISC) PID: 94 SPN: 94 FMI: 0 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.

If the engine will not start and Fault Code 559/2215 becomes active during cranking, but no speed sensor fault codes exist, monitor the fuel rail pressure with INSITE? electronic service tool. If the rail pressure is low, check the following:

1)Fuel system prime (make sure there is fuel in the tanks and the system is primed)
2)Fuel lift pump pressure.
3)Fuel gear pump pressure.

If the gear pump pressure is OK, test for system leakage:

1)High-pressure pump leakage.
2)Injector leakage.
3)Fuel rail pressure relief valve.

If Fault Code 559/2215 is inactive and there are no existing performance complaints, it is possible the vehicle was run out of fuel or the engine was not primed following fuel filter replacement. Clear the inactive fault code.

Fault Code559/ 2215 sets when the engine is running and measured rail fuel rail pressure remains at least 10 Mpa [1450 psi] less than commanded pressure. Once detected, Fault Code 559/2215 will remain active until the engine is turned off or until the measured fuel rail pressure matches the commanded fuel rail pressure. When a condition exists that causes Fault Code 559/2215 to become active, it is typical for the fault code to become active when the engine is heavily loaded and become inactive when the engine is lightly loaded.

When Fault Code 559/2215 occurs, the fuel system has lost its ability to maintain fuel rail pressure.

Possible causes:

1)Excessive fuel inlet restriction
2)Fuel filter plugging
3)Air in the fuel system
4)Fuel gear pump output low
5)Fuel gear pump pressure regulator sticking or leaking
6)High-pressure pump capacity decay (high leakage to drain from the high-pressure pump)
7)Fuel rail pressure relief valve leaks to drain
8)Fuel rail pressure relief valve opens at too low a pressure
9)Injector fuel circuit leaks to drain
10)Pressure sensor reads more than 10 Mpa [1450 psi] lower than actual pressure.

Intermittent ECM power supply connections can cause Fault Code 559/2215. If the engine is running with an active Fault Code 559/2215 and Fault Codes 449 or 2311 are not present, check the ECM power supply for intermittent connections. Fault Code 1117 can also be active if this fault condition exists.

Inactive Fault Code:

Troubleshooting inactive Fault Code 559/2215 can be very difficult. The fault code must be active for any of the outlined procedures in which the engine is operated during the test. For engines with high counts of inactive Fault Code 2215, operate the engine on a chassis dynamometer or a diagnostic road test to duplicate the fault code. The most common causes of intermittent Fault Code 559/2215 that are difficult to create are leaking high-pressure connectors that only leak when the engine and the fuel are hot, and intermittent fuel supply restrictions, such as debris floating in the fuel tank. Check the High Pressure Connector (HPC) and connector torque and torque to specification if necessary. Operate the engine on a chassis dynamometer or conduct a diagnostic road test to duplicate the fault code.

Possible repairs:

1)Add fuel to the fuel tank.
2)Replace or repair the pressure side fuel filter/housing.
3)Replace the lift pump.
4)Replace the lift pump and voltage regulator.
5)Replace the voltage regulator.
6)Inspect the high pressure connector for damage and replace, if necessary.
7)Replace the injector of the cylinder that is contributing to the high return flow.
8)Replace the rail fuel pressure sensor.
9)Replace the EFC actuator valve.
10)Replace the high pressure fuel pump.
2)Replace or repair the pressure side fuel filter/housing.
3)Replace the lift pump.
4)Replace the lift pump and voltage regulator.
5)Replace the voltage regulator.
6)Inspect the high pressure connector for damage and replace, if necessary.
7)Replace the injector of the cylinder that is contributing to the high return flow.
8)Replace the rail fuel pressure sensor.
9)Replace the EFC actuator valve.
10)Replace the high pressure fuel pump.
2)Replace or repair the pressure side fuel filter/housing.
3)Replace the lift pump.
4)Replace the lift pump and voltage regulator.
5)Replace the voltage regulator.
6)Inspect the high pressure connector for damage and replace, if necessary.
7)Replace the injector of the cylinder that is contributing to the high return flow.
8)Replace the rail fuel pressure sensor.
9)Replace the EFC actuator valve.
10)Replace the high pressure fuel pump.