Case IH 19050 (F-3226-31) – Engine Control Unit (ECU) / Engine Management System (EMS) / Aftertreatment Control Module (ACM): Downstream NOx sensor supply voltage is out of range.

The control module has detected that the electrical supply voltage going to the downstream Nitrogen Oxide (NOx) sensor is either too high or too low compared to the expected operating parameters.

• VESTRUM CVX
• Axial-Flow Combines 240 Series (7240, 8240, 9240)
• Magnum Tractors 250, 280, 310, 340, 380
• Wheel Loaders Tier 4B (1021G)
• Farmall Tractors CVT Transmission models

1. 1

   Verify that the machine's battery and alternator are outputting the correct system voltage (a failing alternator or weak batteries can cause out of range voltage codes).

2. 2

   Visually inspect the wiring harness leading to the downstream NOx sensor for melted wires, chafing, or corrosion at the connector pins.

3. 3

   Disconnect the downstream NOx sensor, turn the key to the ON position (engine OFF), and use a multimeter to check the supply voltage pin on the harness side.

4. 4

   Check for an internal sensor short: if the harness voltage is correct when unplugged but drops out of range when plugged in, the NOx sensor likely has an internal short circuit.

1. 1

   Power Down

   Turn off the machine and switch off the main battery disconnect to prevent electrical spikes.

2. 2

   Locate the Sensor

   Locate the downstream NOx sensor. It is threaded into the exhaust pipe directly after the SCR catalyst (DOC/SCR assembly).

3. 3

   Disconnect Wiring

   Unplug the electrical connector for the sensor and unclip the wire routing from any brackets.

4. 4

   Remove the Sensor

   Using a specialized NOx sensor socket or a standard wrench (usually 22mm), carefully unscrew the sensor from the exhaust pipe. Note: Exhaust sensors are prone to seizing. You may need to apply penetrating oil and let it sit before removal.

5. 5

   Install New Sensor

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if it does not come pre-applied). Thread it into the exhaust pipe by hand to prevent cross-threading, then torque to OEM specifications.

6. 6

   Reconnect

   Plug in the electrical connector and secure the wiring harness exactly as it was from the factory to keep it away from extreme exhaust heat.

7. 7

   Clear Codes

   Turn on the battery disconnect, start the engine, and use a diagnostic scan tool (like the CNH Electronic Service Tool) to clear the inactive 19050 fault code. Run the machine to ensure the code does not return.