PACCAR PX-6 CM2150 (2007-09) Fault Code: 553 (ISC/ISL) PID: 157 SPN: 157 FMI: 0 Injector Metering Rail Number 1 Pressure – Data Valid but Above Normal Operating Range – Moderately Severe Level. The ECM has detected that fuel pressure is higher than the commanded pressure.

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.

A fuel pump actuator with excessive leakage or a damaged inboard o-ring will result in high fuel rail pressures at idle or light load.

If the fuel pump actuator exhibits excessive leakage, it is possible that the fuel rail pressure will reach the opening pressure of the fuel rail pressure relief valve and Fault Code 1911 can possibly also become active.

The fuel rail pressure sensor should 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 running. Once the engine is keyed off, there could be a significant amount of time waiting on the rail to depressurize to zero. 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 rail fuel pressure sensor.
2)Repair the source of the high fuel drain line restriction.
3)lace the fuel pump actuator.