PACCAR PX-6 CM2150 (2007-09) Fault Code: 449 (ISC/ISL) 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 fuel rail is higher than the fuel pressure relief valve.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM.

Fault Code 449 is activated when the sensed rail fuel pressure exceeds for several consecutive seconds the opening pressure of the fuel pressure relief valve.

Fault Code 449 is not used to indicate a fuel pressure relief valve opening. It is used to indicate a fuel pressure relief valve which fails to open or does not regulate pressure. Troubleshooting must be focused on inspecting the drain line path of the fuel pressure relief valve for restrictions/obstructions and checking or replacing the fuel pressure relief valve. A restriction in the fuel-drain-tank return line can prevent unneeded fuel from exiting the fuel system. Check the fuel drain line restriction from the fuel rail to the tank for damage.

The fuel rail pressure sensor must also be checked. When checking the fuel rail pressure sensor accuracy, make sure the high-pressure fuel rail is not pressurized. The fuel pump, high-pressure fuel lines, and fuel rail contain very high-pressure fuel. Do not loosen any fittings while the engine is operating. Once the engine is keyed off, there could be a significant amount of time waiting on the rail to depressurize to 0. It is necessary to manually relieve the pressure from the high-pressure fuel rail by loosening the pump to rail line at the rail.

Possible repairs:

1)Replace the drain line or repair the source of the high fuel drain line restriction.
2)Repair the tampering or replace the fuel pressure relief valve.
3)Replace the rail fuel pressure sensor.