Cummins ISB6.7 CM2350 (2013-17) Fault Code: 4279 PID: SPN: 5848 FMI: 21 Aftertreatment 1 SCR Intermediate NH3 – Data not Rational – Drifted Low. An in range low failure has been detected.

Cummins ISB6.7 CM2350 (2013-17) Fault Code: 4279 PID: SPN: 5848 FMI: 21 Aftertreatment 1 SCR Intermediate NH3 – Data not Rational – Drifted Low. An in range low failure has been detected.

Circuit Description
The 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 Location
The aftertreatment SCR intermediate NH3 sensor is located in the middle of the aftetreatment SCR catalyst.

Conditions for Running the Diagnostics
This diagnostic has to meet specific engine and aftertreatment conditions to run and complete. Sensor data is gathered over varying engine speeds and loads. When enough data has been gathered, the diagnostic will run, make a pass/fail decision, and begin to gather data again.

Conditions for Setting the Fault Codes
The Engine Control Module (ECM) detected the aftertreatment SCR intermediate NH3 sensor reading is in range low.

Action Taken When the Fault Code is Active
The 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 Code
It 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).

Possble Causes:
1)A malfunctioning aftertreatment SCR intermediate NH3 sensor probe
2)A malfunctioning aftertreatment SCR intermediate NH3 sensor module