Circuit DescriptionThe engine aftertreatment system monitors the soot load in the aftertreatment diesel particulate filter. Under normal operating conditions, the aftertreatment diesel particulate filter is self-cleaning, where soot is converted to carbon dioxide, nitrogen, and water. Under light load operating conditions, it can be necessary to perform a stationary regeneration of the aftertreatment diesel particulate filter. The soot load in the aftertreatment diesel particulate filter is estimated, using the aftertreatment differential pressure sensor and the calculated soot output of the engine.

Component LocationThe aftertreatment diesel particulate filter is located in the exhaust system and is installed by the original equipment manufacturer (OEM). Refer to the OEM service manual.

Conditions for Running the DiagnosticsThis diagnostic runs continuously when the engine is running.

Conditions for Setting the Fault CodesThe Engine Control Module (ECM) detected the soot load of the aftertreatment diesel particulate filter had exceeded the maximum operating limits.

Action Taken When the Fault Code is ActiveThe ECM illuminates the red STOP ENGINE lamp immediately after the diagnostic runs and fails.Torque output of the engine will be reduced as the soot load in the aftertreatment diesel particulate filter increases.Active and stationary regeneration of the diesel particulate filter will be disabled.Exhaust Gas Recirculation (EGR) valve operation will be disabled.Conditions for Clearing the Fault CodeUse INSITE™ electronic service tool to perform the Diesel Particulate Filter Reset procedure found under the Aftertreatment Maintenance section of Advanced ECM Data.After completing a stationary regeneration (as instructed in this fault code troubleshooting tree) and no additional faults become active, the repair has been validated.

The ECM will turn off the red STOP ENGINE lamp immediately after the diagnostic runs and passes.

Shop TalkNote: Repeated occurrences of this fault code may indicate the engine requires frequent regeneration. Refer to symptom tree t147 (Aftertreatment Diesel Particulate Filter-Excessive Automatic and/or Stationary Regeneration) to identify the cause of frequent regeneration.

Possible causes of this fault code include:

The aftertreatment wiring harness or the aftertreatment temperature sensor connector pin installation may be incorrect.The engine has been operating in a light load condition that prevents exhaust temperatures from being high enough to actively regenerate the aftertreatment diesel particulate filter.A possible base engine malfunction that causes excessive black soot to be generated.If both Fault Code 1921 and 2777 are inactive with an active Fault Code 1922, this indicates that a regeneration inhibit message has been received by the engine ECM and that active regeneration of the aftertreatment diesel particulate filter was not allowed. Use the OEM manuals to confirm that the OEM settings for the aftertreatment permit switch are configured correctly.

Possible Cause:1) Aftertreatment DPF differential pressure sensor failure2) DPF failure3) ECM calibration