Cummins ISX11.9 CM2250 (2010-12) Fault Code: 295 (X) PID: 108 SPN: 108 FMI: 2 Barometric Pressure- Data Erratic, Intermittent, or Incorrect

Circuit Description
The barometric pressure sensor responds to pressure changes in the atmospheric pressure. The pressure changes occur based on the elevation where the engine is presently operating. The barometric 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 barometric pressure sensor on the sensor supply 2 circuit. The ECM also provides a ground on the sensor return circuit. The barometric pressure sensor provides a signal to the ECM on the barometric pressure sensor signal circuit. This sensor signal voltage changes, based on the pressure of the atmosphere. The ECM will detect a low signal voltage when the vehicle is operating at high altitudes. The ECM will detect a high signal voltage when the vehicle is operating at sea level altitudes.

Component Location
The barometric pressure sensor is mounted on the main branch of the engine harness near the ECM.

Conditions for Running the Diagnostics
This diagnostic consists of two parts.

One part runs immediately after the keyswitch is turned OFF, and the engine coolant temperature is above 70?C or 158?F.
The other part runs continuously when the engine is operating.
Conditions for Setting the Fault Codes
The ECM detects that the barometric pressure reading is higher or lower than the other absolute pressure sensors on the engine, or an in-range malfunction of the sensor has been detected.

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.
A default value of the ambient pressure reading is used.
Diesel exhaust fluid injection into the aftertreatment system is disabled.
Active and stationary regeneration of the diesel particulate filter will be disabled.
The exhaust gas recirculation (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, first ensure the engine coolant temperature is above 70?C or 158?F. Operate the engine if necessary.
Cycle the keyswitch to the ON position for 30 seconds, then cycle the keyswitch to the OFF position for 30 seconds. Start the engine and let it idle for 30 seconds.
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 engines.

Shop Talk
After key OFF when the engine is warm, the sensor readings for various engine pressure sensors on the engine are compared with the barometric pressure. This fault code occurs if the barometric pressure sensor reading is different from the other sensor readings. This fault can also be set if a barometric pressure reading higher or lower than what is possible is detected.

Possible causes of this fault code include:

Malfunctioning barometric pressure sensor
High resistance in the barometric pressure sensor signal or return lines.
Plugged or highly restricted air filter can also possibly cause this fault to become active, especially at higher altitudes.

Possible Cause:
1) ECM failure