Cummins ISB4.5 CM2150 Fault Code: 1887 PID: 2202 SPN: 3226 FMI: 4 Aftertreatment Outlet NOx Sensor Circuit – Voltage Below Normal or Shorted to Low Source.

Circuit Description
The aftertreatment outlet nitrogen oxides (NOx) sensor is a smart device and receives commands from the engine electronic 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 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 catalyst.

Conditions for Running the Diagnostics
This diagnostic runs when the exhaust gas temperature at the aftertreatment intake NOx sensor is above 150°C [302°F] and the engine is running.

Conditions for Setting the Fault Codes
An internal circuit error has been detected by in the aftertreatment outlet NOx sensor assembly.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE lamp and/or the malfunction indicator lamp (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 and operate the engine to raise exhaust temperatures.
-The exhaust gas temperature at the aftertreatment outlet NOx sensor must be above 150°C [302°F] before the sensor can run its internal diagnostics
-The ECM will turn off the amber CHECK ENGINE lamp and/or MIL immediately after the diagnostic runs and passes.
-Use INSITE™ electronic service tool to verify the fault code is inactive.
-The inactive fault code will be cleared from the memory after 9600 hours of engine operation without a reoccurrence.

Possible Causes
-For 12 Volt Systems: The voltage supplied to the aftertreatment outlet NOx sensor is below + 11-VDC or above 14-VDC.
-For 24 Volt Systems: The voltage supplied to the aftertreatment outlet NOx sensor is below + 18-VDC or above + 32-VDC.
-The aftertreatment outlet NOx sensor has malfunctioned or is damaged
-The aftertreatment outlet NOx sensor internal heater has malfunctioned
-The NOx sensor part number is incorrect.

*Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.