From the manual:
The aftertreatment diesel particulate filter is designed to physically filter soot and to eliminate hydrocarbons from the engine exhaust gases through catalyst reactions in the exhaust stream. Federal law requires that the filter’s efficiency be monitored for signs of degradation that would compromise the efficiency of the filter. The ECM monitors the efficiency of the aftertreatment diesel particulate filter via interpretation of data received from the Diesel Particulate Filter Pressure Sensor, which monitors the restriction across the aftertreatment diesel particulate filter. The ECM monitors the restriction in the aftertreatment diesel particulate filter at various engine speeds/loads and will set the fault if the restriction is below a calibrated threshold minimum value. The ECM will illuminate the MIL light Immediately when the diagnostic runs and fails in two consecutive drive cycles. Active regeneration of the aftertreatment Diesel particulate filter will also be disabled for the remainder of the drive cycle. The ECM will try to regenerate the aftertreatment diesel particulate filter on the next subsequent drive cycle. The ECM will turn off the MIL light immediately after the diagnostic runs and passes in four consecutive drive cycles.
This diagnostic runs when the engine is running and after an active regeneration of the aftertreatment diesel particulate filter has completed.
The ECM will set the fault if the diagnostic fails in two consecutive drive cycles.
FAILED DIESEL PARTICULATE FILTER PRESSURE SENSOR
FAILED AFTERTREATMENT DIESEL PARTICULATE FILTER
EXHAUST SYSTEM LEAK
EXHAUST PRESSURE SENSOR 1/2
SWAPPED OR LEAKING PARTICULATE FILTER PRESSURE SENSOR LINES