Cummins ISB4.5 CM2150 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 and communicates with the engine ECM via the J1939 data link. The aftertreatment outlet NOx sensor receives power and a ground directly from the battery. The aftertreatment outlet NOx sensor performs its own internal diagnostics and reports malfunctions back to the primary engine ECM via the J1939 data link. The aftertreatment outlet NOx sensor is used to measure the outlet NOx emissions from the engine.

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. The NOx sensor is permanently attached to the NOx control module. They are serviced as a single component and can not be replaced individually.

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 ECM loses J1939 communications with the aftertreatment outlet NOx sensor.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE lamp and/or the MIL immediately after the diagnostic runs and fails.
-Engine torque will be reduced.

Conditions for Clearing the Fault Code
-This fault code can not be cleared with INSITE™ electronic service tool.
-To validate the repair, start the engine and let it idle for 1 minute.
-The ECM will turn off the amber CHECK ENGINE light and/or MIL immediately after the diagnostic runs and passes.
-Use INSITE™ electronic service tool to verify that the fault code is inactive.
-The inactive fault code will be cleared from memory after 9600 hours of engine operation without a re-occurance.

Possible Causes
-The aftertreatment outlet NOx sensor is not receiving power from the battery supply circuit in the OEM harness. This could 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 ECM and aftertreatment outlet NOx sensor.
-Intermittent communications between the aftertreatment outlet NOx sensor and the primary engine ECM on the J1939 data link.
-A damaged engine ECM.