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Cummins X15 CM2450 X124B (2018 & Newer) Fault Code: 6925 PID: SPN: 3216 FMI: 11/31 Aftertreatment 1 SCR Intake NOx Sensor – Condition Exists


An incorrect NOx sensor reading has been detected by the aftertreatment intake NOx sensor.

Possible reduced engine performance.

Circuit Description:
The aftertreatment intake NOx (Nitrogen Oxides) sensor is a smart device and communicates with the Engine Control Module (ECM) via the J1939 data link. The aftertreatment intake NOx sensor performs 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:
1. This diagnostic runs when the aftertreatment diesel oxidation catalyst intake temperature sensor has been above 150°C [302°F] for 5 minutes while the engine is running.
2. This diagnostic has to meet specific engine and aftertreatment conditions to run and complete.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the aftertreatment intake NOx reading was higher or lower than the calculated aftertreatment intake NOx value for the engine operating conditions.

Action Taken When the Fault Code is Active:
The ECM illuminates the amber check engine lamp and/or Malfunction Indicator Lamp (MIL) after the diagnostic fails on two consecutive trips.

Conditions for Clearing the Fault Code:
1. To validate the repair, it may be necessary to operate the vehicle on a chassis dynamometer or to drive the vehicle in order to get the engine load high enough for the diagnostic to run.
2. The fault code status displayed by the diagnostic tool will change to inactive immediately after the diagnostic runs and passes.
3. The ECM will turn off the amber check engine lamp immediately after the diagnostic runs and passes.
4. For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
5. The reset all faults command in the diagnostic 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:
1. EGR system leaks.
2. Exhaust system leaks.
3. An incorrectly installed aftertreatment intake NOx sensor.
4. An aftertreatment intake NOx sensor that has carbon buildup on the tip of the sensor.
5. A malfunctioning EGR differential pressure sensor.
6. A malfunctioning EGR valve.
7. Excessive oil consumption.
8. Possible engine misfire.
9. The NOx sensor part number is incorrect.