Cummins ISX12 CM2250 (2010-12) Fault Code: 2771 PID: SPN: 3226 FMI: 9 Aftertreatment Outlet Nox Sensor- Abnormal Update Rate

Circuit Description
The aftertreatment outlet NOx (nitrogen oxides) sensor is a smart device that communicates with the engine control module via the J1939 data link. The aftertreatment outlet NOx sensor performs its own internal diagnostics and reports malfunctions back to the primary engine control module 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 aftertreatment SCR catalyst.

Conditions for Running the Diagnostics
This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes
This fault code is triggered when the internal engine control module loses J1939 communications with the aftertreatment outlet NOx sensor.

Action Taken When the Fault Code is Active
The engine control module illuminates the amber CHECK ENGINE light and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.
Engine torque will be reduced if the engine is operated for a limited period of time with the fault code active.
Engine torque will be severely reduced and vehicle speed will be limited to 8 km [5 mi] per hour after extended engine operation with the fault code active.
Conditions for Clearing the Fault Code
To validate the repair, start the engine and let it idle for 1 minute.
The fault code status displayed by INSITE? electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
The engine control module will turn off the amber CHECK ENGINE lamp after the diagnostic runs and passes.
For On-Board Diagnostic (OBD) engines, the engine control module will turn off the MIL after 3 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 Talk
Possible causes of this fault code include:

The Aftertreatment Outlet NOx Sensor is not receiving power from the battery supply circuit in the OEM harness. This can be caused by an open circuit in the power supply wire, blown NOx sensor fuse, or low voltage supplied by the battery.
Open return circuit on the aftertreatment outlet NOx sensor battery return.
Open or short circuit on the J1939 data link circuit between the engine control module and aftertreatment outlet NOx sensor.
Intermittent communications between the aftertreatment outlet NOx sensor and the primary engine control module on the J1939 data link.
A damaged engine control module.
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 failure
2) Loose Connections
3) VGT actuator failure
4) ECM calibration