Case IH 3901 – Engine Control Module (ECM) / EDC (Electronic Diesel Control): NOx Sensor (CAN): NOx Sensor detects incorrect supply

This code indicates that the Nitrogen Oxide (NOx) sensor is receiving an incorrect power supply voltage. The sensor communicates via the CAN bus, and its internal diagnostics have flagged that the electrical supply it relies on to operate (and heat the sensor element) is outside of the expected or required range.

• Puma
• Magnum
• Steiger
• SV340

1. 1

   Check Vehicle Supply Voltage: Ensure the machine's battery and alternator are providing the correct system voltage, as low or spiking voltage can trigger supply errors.

2. 2

   Inspect the Wiring Harness: Visually inspect the wiring harness leading to the NOx sensor for chafing, breaks, or melted sections.

3. 3

   Check Connectors: Disconnect the NOx sensor and check the pins for corrosion, moisture, or loose connections.

4. 4

   Test Power and Ground: Use a multimeter to verify that the correct supply voltage and a solid ground are reaching the sensor connector.

5. 5

   Evaluate the Sensor: If the wiring harness, fuses, and vehicle supply voltage test perfectly, the fault is likely an internal failure of the NOx sensor's own control module.

1. 1

   Turn off the machine's ignition and disconnect the battery to prevent electrical shorts.

2. 2

   Locate the affected NOx sensor on the exhaust aftertreatment system.

   Note: there are typically upstream/pre-SCR and downstream/post-SCR sensors; verify which one is logging the error if multiple codes are present.

3. 3

   Disconnect the sensor's electrical connector from the main engine wiring harness.

4. 4

   If the wiring harness is damaged, repair the wiring. If the wiring is intact, proceed to replace the sensor.

5. 5

   Apply penetrating fluid to the base of the NOx sensor if it is seized in the exhaust pipe.

6. 6

   Use a specialized NOx/O2 sensor wrench to carefully unthread the sensor from the exhaust system.

7. 7

   Install the new NOx sensor and tighten it to the manufacturer's torque specifications.

8. 8

   Reconnect the electrical connector and secure the cable to prevent it from resting on hot exhaust components.

9. 9

   Reconnect the battery.

10. 10

    Connect a diagnostic tool (such as the CNH Electronic Service Tool) to clear the fault codes and run the engine to operating temperature to verify the repair.