Cummins ISB4.5 CM2150 Fault Code: 1881 PID: SID 324 SPN: 3251 FMI: 4 Aftertreatment Diesel Particulate Filter Differential Pressure Sensor Circuit – Voltage Below Normal, or Shorted to Low 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 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 less than 0.25-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 of the aftertreatment diesel particulate filter differential pressure is used.

Shop Talk
Verify 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
-Signal circuit open or shorted to ground in the engine harness or sensor.
-Supply line open or shorted to ground.