Cummins X12 CM2350 X119B (2018 & Newer) Fault Code: 3934 PID: SPN: 5851 FMI: 2 Aftertreatment 1 SCR Intermediate NH3 Gas Sensor Power Supply- Data Erratic, Intermittent, or Incorrect

Circuit Description
The aftertreatment SCR intermediate NH3 (ammonia) sensor is a smart device that communicates with the engine control module via the J1939 data link. The aftertreatment intermediate NH3 sensor performs its own internal diagnostics and reports malfunctions back to the primary engine control module using the J1939 data link. The aftertreatment intermediate NH3 sensor is used to measure the ammonia in the aftertreatment system.

Component Location
The aftertreatment SCR intermediate NH3 sensor is located in the middle of the aftetreatment SCR catalyst.

Conditions for Running the Diagnostics
This diagnostic runs when the aftertreatment SCR intermediate temperature has been above 170 C [338 F] for a calibratible period of time while the engine is running.

Conditions for Setting the Fault Codes
The Engine Control Module (ECM) detected an intermittent battery voltage supply to the aftertreatment SCR intermediate NH3 sensor resulting in an internal reset of the sensor.

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.

Diesel exhaust fluid injection into the aftertreatment system is disabled.
Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.
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 aftertreatment SCR intermediate temperature must be above 170 C [338 F] for 5 seconds before the aftertreatment SCR intermediate NH3 sensor can run 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 immediately after the diagnostic runs and passes.
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.
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 ECM detects an internal reset of the sensor. This internal reset is caused by an intermittent battery voltage supply. This fault code indicates that an intermittent wiring problem has been detected. All wiring and connectors should be closely inspected for intermittent connections.

Possible Cause:
1) Loose Connections
2) OEM harness
3) ECM calibration