Cummins ISX12 CM2250 (2010-12) Fault Code: 221 (X) PID: 108 SPN: 108 FMI: 3 Barometric Pressure Sensor Circuit- Voltage Above Normal or Shorted to High Source

Circuit Description
The ambient air 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 ambient air pressure sensor has a 5 volt supply circuit, a sensor signal voltage, and a return circuit.

The ambient air pressure sensor provides a signal to the ECM on the ambient air 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.

NOTE: Some engines use a combination turbocharger compressor intake pressure/temperature sensor located in the OEM intake air plumbing to determine barometric pressure rather than a barometric pressure sensor. Refer to the engine wiring diagram to determine which sensor the engine is equipped with.

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 ambient air pressure signal voltage is greater than 4.75-VDC for more than 10 seconds.

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 for 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 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 Diagnostics (OBD) engines, the ECM will turn off the MIL after three consecutive trips where the diagnostic runs and passes.
This fault code and the MIL can also be cleared with INSITE? electronic service tool.
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
The barometric pressure sensor shares supply and return wires in the engine harness with other sensors. Opens and shorts in the engine harness can cause multiple fault codes to be active. Before troubleshooting Fault Code 221, check for multiple faults.

Possible causes of this fault code include:

Open return circuit in the harness, connectors, or sensor.
Signal circuit shorted to sensor supply or battery voltage.

Possible Cause:
1) ECM failure
2) Engine Harness