Reason:
Aftertreatment Diesel Particulate Filter Differential Pressure – Data Valid But Above Normal Operating Range – Most Severe Level. The soot load of the aftertreatment diesel particulate filter has exceeded the recommended limits. Engine protection derate is enabled.

Effect:
Possible reduced engine performance

Circuit Description:
The 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 Location:
The 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 Diagnostics:
This diagnostic runs continuously when the engine is running.

Conditions for Setting the Fault Codes:
The 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 Active
1) The ECM illuminates the red STOP ENGINE lamp immediately after the diagnostic runs and fails.
2) Torque output of the engine will be reduced as the soot load in the aftertreatment diesel particulate filter increases.
3) Active and stationary regeneration of the diesel particulate filter will be disabled.
4) Exhaust Gas Recirculation (EGR) valve operation will be disabled.

Conditions for Clearing the Fault Code:
1) Use INSITE™ electronic service tool to perform the Diesel Particulate Filter Reset procedure found under the Aftertreatment Maintenance section of Advanced ECM Data.
2) To validate the repair, start the engine and perform the INSITE™ electronic service tool Aftertreatment Diesel Particulate Filter Regeneration Test.
3) The ECM will turn off the red STOP ENGINE lamp immediately after the diagnostic runs and passes.

Shop Talk:
Note: 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.

Use the OEM manuals to confirm that the OEM settings for the aftertreatment permit switch are configured correctly.

Possible Causes:
1) The aftertreatment wiring harness or the aftertreatment temperature sensor connector pin installation may be incorrect.
2) 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.
3) A possible base engine malfunction that causes excessive black soot to be generated.
4) 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.