Cummins ISX12 CM2250 (2010-12) Fault Code: 3725 PID: 102 SPN: 3216 FMI: 10 Aftertreatment Intake Nox Sensor- Abnormal Rate of Change

Circuit Description
The aftertreatment intake NOx sensor is a smart device that receives commands from the engine control module (ECM) via the J1939 data link. The aftertreatment intake 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 intake NOx sensor is used to measure the NOx emissions at the intake of the aftertreatment system.

Component Location
The aftertreatment intake NOx sensor is mounted on the engine near the turbocharger turbine outlet.

Conditions for Running the Diagnostics
This diagnostic operates when the diesel oxidation catalyst (DOC) intake temperature at the aftertreatment intake NOx sensor is above 200?C [392?F] and the engine is operating.

Conditions for Setting the Fault Codes
The aftertreatment intake NOx sensor reading is not valid.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE lamp and/or the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.
Conditions for Clearing the Fault Code
To 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. Use INSITE? electronic service tool.
The DOC intake temperature at the aftertreatment intake NOx sensor must be above 200?C [392?F] before the sensor can perform 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 after the diagnostic runs and passes.
For On-Board Diagnostics (OBD) engines, the ECM will turn off the 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 Talk
This fault code sets when the aftertreatment intake NOx sensor indicates to the ECM that it is not providing valid data.
Troubleshoot the aftertreatment intake NOx sensor for Fault Codes 1885, 3232, or 3682 before troubleshooting this fault code.
Reference the appropriate original equipment manufacturer (OEM) wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

For intermittent power supply and data link 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) ECM calibration