Circuit DescriptionThe 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 LocationThe 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 DiagnosticsThis diagnostic runs when the aftertreatment SCR outlet temperature has been above 200°C [392° F] for 60 seconds while the engine is running.

Conditions for Setting the Fault CodesThe Engine Control Module (ECM) detected the power supply to the outlet NOx sensor was above or below a calibratible threshold.

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 CodeTo validate the repair, start and operate the engine to raise exhaust temperatures. This can be done by either driving the vehicle or initiating a stationary regeneration using INSITE™ electronic service tool.The aftertreatment SCR outlet temperature must be above 200° C [392° F] for 60 seconds before the aftertreatment outlet NOx sensor can run its internal diagnostics.The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop TalkPossible causes of this fault code include:

Short to battery or ground in the OEM harnessOpen NOx sensor power supply circuit in the OEM harnessIncorrect system voltage set-up in INSITE™ electronic service toolInternal malfunction of the outlet NOx sensorThe NOx sensor part number is incorrect.Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

For intermittent power supply and datalink communication issues with Aftertreatment Components, it is highly recommended that the OEM Power Distribution Center fuses and relays be thoroughly checked for loose, missing or intermittent connections.

Possible Cause:1) Aftertreatment Outlet NOx sensor failure2) Loose Connections3) Battery failure4) OEM harness5) ECM calibration