Cummins ISB6.7 CM2350 (2013-17) Fault Code: 4452 PID: SPN: 520668 FMI: 31 Aftertreatment Outlet NOx Sensor Closed Loop Operation – Condition Exists. The maximum dosing adjustment has been reached.

Cummins ISB6.7 CM2350 (2013-17) Fault Code: 4452 PID: SPN: 520668 FMI: 31 Aftertreatment Outlet NOx Sensor Closed Loop Operation – Condition Exists. The maximum dosing adjustment has been reached.

Circuit Description
The aftertreatment outlet NOx (nitrogen oxides) sensor is a smart device and communicates with the engine control module (ECM) via the J1939 data link. The aftertreatment outlet NOx sensor performs its own internal diagnostics and reports malfunctions back to the primary ECM using the J1939 data link. The NOx sensor is permanently attached to the NOx control module. They are serviced as a single component and can not be replaced individually. The aftertreatment outlet NOx sensor is used to measure the NOx emissions at the outlet of the aftertreatment system.

Component Location
The aftertreatment outlet NOx sensor location can vary depending on engine application. It is usually located in the exhaust system at the outlet of the selective catalytic reduction (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 adjusted aftertreatment diesel exhaust fluid dosing command based on the aftertreatment outlet NOx sensor has reached a maximum limit.

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).

Possible causes:
1)A malfunctioning aftertreatment outlet NOx sensor
2)A malfunctioning aftertreatment diesel exhaust fluid dosing unit
3)A malfunctioning SCR catalyst