Cummins ISB CM850 (2003-06) Fault Code: 449 (Auto) PID: 94 SPN: 157 FMI: 0 Injector Metering Rail Number 1 Pressure – Data Valid But Above Normal Operating Range – Most Severe Level. The ECM has detected that fuel pressure in the rail fuel is higher than the commanded pressure.

Fault Code 449 is activated when the sensed rail fuel pressure reaches the opening pressure of the rail fuel pressure relief valve. Sensed pressure has exceeded system target range.

An electric fuel control actuator with excessive leakage will result in high rail fuel pressures at idle or light load, and Fault Code 449 can possibly be logged. A restriction in the fuel-drain-to-tank return line can prevent unneeded fuel from exiting the high-pressure fuel pump. This excess drain fuel can enter the pumping chamber and pressurize the rail. Check the fuel drain line restriction. High resistance or an open circuit in the electric fuel control actuator can cause this fault to log (though Fault Codes 272 and 2311 will become active in these cases). Air in the fuel can result in pressure changes that would cause this fault to log very high. High lift pump delivery pressure could cause this fault to log, as could tampering with the rail fuel pressure sensor.

Possible repairs:

1)Replace the sensor or repair the engine harness.
2)Replace the electric fuel lift pump.
3)Replace the electronic fuel control valve.
4)Repair or replace the fuel return drain line.
5)Replace the high-pressure fuel pump.
6)Replace the fuel rail pressure relief valve.