Circuit DescriptionThe aftertreatment SCR intermediate NH3 (ammonia) sensor is a smart device that communicates with the engine control module via the J1939 data link. The aftertreatment intermediate NH3 sensor performs its own internal diagnostics and reports malfunctions back to the primary engine control module using the J1939 data link. The aftertreatment intermediate NH3 sensor is used to measure the ammonia in the aftertreatment system.

Component LocationThe aftertreatment SCR intermediate NH3 sensor is located in the middle of the aftetreatment SCR catalyst.

Conditions for Running the DiagnosticsThis diagnostic has to meet specific engine and aftertreatment conditions to run and complete.

Conditions for Setting the Fault CodesThe Engine Control Module (ECM) detected the aftertreatment SCR intermediate NH3 sensor reading is not changing.

Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE lamp and/or Malfunction Indicator Lamp (MIL) after the diagnostic fails on two consecutive trips.

Conditions for Clearing the Fault CodeIt is necessary to use the “Reset All Faults” command in INSITE™ electronic service tool to clear this fault and extinguish the amber CHECK ENGINE lamp and/or Malfunction Indicator Lamp (MIL).

Shop TalkPossible causes of this fault code include:

A malfunctioning aftertreatment SCR intermediate NH3 sensor probe

Possible Cause:1) Aftertreatment DEF dosing valve failure2) Aftertreatment NH3 sensor probe failure3) ECM calibration