Cummins X12 CM2350 X119B (2018 & Newer) Fault Code: 7866 PID: SPN: 108 FMI: 10/10 Barometric Pressure – Abnormal Rate of Change

Lamp:
Amber

Reason:
An error in the barometric pressure sensor signal was detected by the ECM.

Effect:
Possible reduced engine performance.

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.

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

Conditions for Running the Diagnostic:
This diagnostic runs immediately after the keyswitch is turned OFF.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the barometric pressure reading was higher or lower than the other absolute pressure sensors on the engine, or an in-range malfunction of the sensor was detected.

Action Taken When the Fault Code is Active:
1. The ECM illuminates the amber check engine lamp and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.
2. A default value for the barometric pressure reading is used.
3. Exhaust Gas Recirculation (EGR) valve operation will be disabled.
4. Diesel exhaust fluid injection into the aftertreatment system is disabled.
5. 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:
1. To validate the repair, start the engine, let it idle for 1 minute, and then shutdown the engine.
2. The ECM will turn off the amber check engine lamp immediately after the diagnostic runs and passes.
3. 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.
4. The “reset all faults” command in the recommended diagnostic tool or equivalent 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 barometric air pressure sensor.