Cummins ISX12 CM2250 (2010-12) Fault Code: 451 PID: SPN: 157 FMI: 3 Injector Metering Rail 1 Pressure Sensor Circuit- Voltage Above Normal or shorted to High Source

Circuit Description
The fuel rail pressure sensor responds to pressure changes in the fuel delivered to the fuel rail. The fuel rail pressure sensor has a 5 volt supply circuit, a sensor signal voltage, and a return circuit.

The electronic 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 signal to the ECM on the fuel rail pressure sensor signal 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 fuel pressure sensor is installed in the fuel rail.

Conditions for Running the Diagnostics
This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes
The ECM detects that the fuel rail pressure signal voltage is greater than 4.75-VDC for more than 3 seconds.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE light and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.
A default value for the fuel rail pressure reading is used.
Active and stationary regeneration of the diesel particulate filter will be disabled.
The EGR valve will be closed.
Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.
Conditions for Clearing the Fault Code
To validate the repair, 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 after the diagnostic runs and passes.
For On-Board Diagnostic (OBD) engines, the ECM will turn off the 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
Causes for this fault code include:

Voltage (+5-VDC or higher shorted to the signal wire)
Open circuit on the signal wire
Open circuit on the 5 Volt supply wire
Open circuit on the return wire
Malfunctioning sensor
Malfunctioning ECM.

Possible Cause:
1) ECM failure
2) Engine Harness
3) ECM calibration