Diagnostic Overview
Cummins fault code 1881 commonly points to an aftertreatment DPF differential pressure sensor circuit problem, often a low-voltage, open-circuit, or signal issue. The ECM uses this sensor to measure restriction across the diesel particulate filter and determine soot load and regeneration needs. Causes may include a failed differential pressure sensor, damaged wiring, loose connector, plugged or cracked pressure tubes, moisture in the sensor lines, or corrosion at the sensor connector. Diagnosis should include inspecting the sensor harness, checking the pressure tubes, comparing live sensor data, and confirming the circuit before condemning the DPF.