Cummins ISX11.9 CM2250 (2010-12) Fault Code: 3748 PID: SPN: 3216 FMI: 20 Aftertreatment Intake Nox Sensor- Data Not Rational- Drifted High

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 engine-out NOx emissions.

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

Conditions for Running the Diagnostics
This diagnostic consists of two parts. The first part of the diagnostic performs when the diesel oxidation catalyst (DOC) intake temperature at the aftertreatment intake NOx sensor is above 200?C [392?F], and the engine is in a motoring condition. The second part of the diagnostic performs when the DOC intake temperature at the aftertreatment intake NOx sensor is above 200?C [392?F] and the calculated NOx value is changing.

Conditions for Setting the Fault Codes
The ECM has detected the aftertreatment intake NOx sensor reading is not zero during motoring conditions for two consecutive trips or the ECM has detected the aftertreatment intake NOx sensor reading is not changing with engine conditions for two consecutive trips.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE lamp immediately and/or malfunction indicator lamp (MIL) after the diagnostic runs and fails on two consecutive trips.
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 using 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
Possible causes of this fault code include:

Malfunctioning aftertreatment intake NOx sensor
Improperly installed aftertreatment intake NOx sensor.

Possible Cause:
1) Aftertreatment Intake NOx Sensor failure
2) ECM calibration