PACCAR PX-8 CM2150 (2007-09) Fault Code: 1911 (ISC/ISL) PID: 157 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.

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, calibrate the ECM.
Fault Code 1911 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.

In normal engine operation, the ECM calibration varies the flow commanded to the fuel pump actuator to achieve the correct fuel rail pressure. System failures that cause loss of pressure control can cause the fuel rail pressure relief valve to open. The fuel rail pressure relief valve acts to protect the high-pressure components from over-pressurization. If the ECM detects that the fuel rail pressure relief valve is open without detection of a fuel pump actuator circuit error, Fault Code 1911 will become active. On certain applications, the ECM will attempt to reset automatically causing a momentary loss of power for less than 1 second.

Conditions that can cause Fault Code 1911:

1)Purging air through the fuel system can cause a pressure overshoot, therefore causing Fault Code 1911 to log. A few bubbles exiting the line during the air in fuel test is expected. A foamy appearance is an indication of a leak that allows air to enter, a severe inlet restriction that causes cavitation, or a system that is not yet primed.
2)Sustained periods of very low pressure under load followed by pressure recovery overshoot. This can be caused by high restriction due to plugged filters (Fault Code 559).
3)A tampered fuel pressure sensor that reads low, a biased pressure sensor, or a poor electrical connection.
4)If an intermittent electrical circuit problem with the fuel pump actuator circuit exists, it is possible for Fault Code 1911 to become active, then inactive during normal engine operation. ECM Fault Code 2311 is designed to detect electrical circuit issues with the actuator. Therefore, it is only necessary to inspect for bad connectors or harness issues for Fault Code 1911 if no other fault codes exist. An electric fuel control actuator with excessive leakage will result in high rail fuel pressures at idle or light load.
5)Other conditions include ECM wiring harness issues such as poor grounds, battery voltage spikes, electrical noise, low alternator output, and large disturbances of battery voltage, as when jump-starting the vehicle.
6)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. Wait at least 10 minutes after shutting down the engine before loosening any fittings in the high-pressure fuel system to allow pressure to decrease to a lower level. There could be a significant amount of time waiting on the rail to depressurize to zero on some engines. In such cases, it may be necessary to manually relieve the pressure from the high-pressure fuel rail.

Possible repairs:

1)Replace the rail fuel pressure sensor.
2)Replace the fuel pump actuator. Use the following procedure for the correct tightening sequence.
3)Repair missing or degraded ground connections.