Cummins X12 CM2350 X119B (2018 & Newer) Fault Code: 4726 PID: SPN: 1239 FMI: 16 Engine Fuel Leakage- Data Valid But Above Normal Operating Range- Moderately Severe Level

Circuit Description
The engine control module (ECM) provides a 5 volt supply to the fuel rail pressure sensor using a dedicated sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The fuel rail pressure sensor provides a primary fuel pressure signal to the ECM on the fuel rail pressure sensor signal 1 circuit. The sensor also provides a secondary fuel pressure sensor signal on the fuel rail pressure signal 2 circuit. This sensor signal voltage changes based on the pressure in the fuel rail. The ECM will detect a high signal voltage at high rail pressure conditions. The ECM will detect a low signal voltage during low rail pressure conditions.

Component Location
The high-pressure fuel pump is mounted to the gear housing. The fuel pump actuator is mounted on the fuel pump. The fuel pressure sensor is mounted in the high pressure fuel rail. The fuel pressure relief valve is mounted on the high pressure fuel rail.

Conditions for Running the Diagnostics
This diagnostic runs periodically during engine operation.

Conditions for Setting the Fault Codes
The Engine Control Module (ECM) detected the engine fuel rail pressure decayed more than expected during a motoring (non-fueling) condition.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE lamp and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.
Conditions for Clearing the Fault Code
It is necessary to use the “Reset All Faults” command in INSITE™ electronic service tool to clear this fault and extinguish the amber CHECK ENGINE lamp and/or Malfunction Indicator Lamp (MIL).

Shop Talk
Possible causes of this fault code include:

Leaking fuel injectors and or fuel injector connectors
Leaking fuel rail pressure relief valve

Possible Cause:
1) Fuel pressure relief valve failure
2) High-pressure fuel pump head failure
3) ECM calibration