CM870 and ISX Engines – FAULT CODE 221

Barometric Pressure Sensor Circuit


Fault Code: 221
PID: P108
SPN: 108
FMI: 3/3
LAMP: Amber

Barometric Pressure Sensor – shorted high. High signal voltage detected at barometric pressure circuit.

Engine power derate.

Barometric Pressure Sensor Circuit

Circuit Description

The barometric pressure sensor is used by the electronic control module (ECM) to monitor the barometric pressure. This value is one of many inputs used by the ECM to determine the correct air/fuel ratio for proper engine operation.

Component Location

The barometric pressure sensor is mounted on the main branch of the engine harness near the ECM. Refer to Section E for a detailed component location view.

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.

Refer to Troubleshooting Fault Code t05-221

Last Modified:  01-Sep-2010