Cummins ISB4.5 CM2150 Fault Code: 1879 PID: SID 324 SPN: 3251 FMI: 3 Aftertreatment Diesel Particulate Filter Differential Pressure Sensor Circuit – Voltage Above Normal or Shorted to High Source.

Circuit Description
The engine control module (ECM) provides a 5 volt supply to the aftertreatment diesel particulate filter differential pressure sensor on the sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The aftertreatment diesel particulate filter differential pressure sensor provides a signal to the ECM on the aftertreatment diesel particulate filter differential pressure sensor signal circuit. This sensor signal voltage changes based on the differential pressure across the aftertreatment diesel particulate filter.

Component Location
The aftertreatment diesel particulate filter differential pressure sensor is located in the aftertreatment system. Refer to the original equipment manufacturer (OEM) troubleshooting and repair manual for exact location of the aftertreatment system.

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 aftertreatment diesel particulate filter differential pressure signal voltage is greater than 4.75-VDC for more than 1 second.

Action Taken When the Fault Code is Active
-The ECM illuminates the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.
-A default value for the aftertreatment diesel particulate filter differential pressure is used.

Conditions for Clearing the Fault Code
The ECM will turn off the MIL immediately after the diagnostic runs and passes.

Shop Talk
Verify the ECM calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM.

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