Cummins X15 CM2450 X124B (2018 & Newer) Fault Code: 4691 PID: SPN: 5585 FMI: 18 Engine Injector Metering Rail 1 Cranking Pressure- Data Valid But Below 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 when the engine is being started.

Conditions for Setting the Fault Codes
The Engine Control Module (ECM) detected the fuel rail pressure during cranking was too low for the engine to start.

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.
The engine may not start.
Conditions for Clearing the Fault Code
To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk
Possible causes of this fault code include:

A malfunctioning fuel lift pump
Low fuel gear pump output pressure
Malfunctioning high-pressure fuel pump
Leaking fuel rail pressure relief valve
Leaking fuel injectors and or fuel injector connectors

Possible Cause:
1) Loose Injector High-Pressure connector
2) Fuel rail pressure relief valve failure
3) High-Pressure fuel pump head failure
4) ECM calibration