Case IH 19051 (F-3223-05) – Engine Control Unit (ECU) or Dosing Control Unit (DCU): Upstream NOx sensor internal failure (Heater Open Circuit Error)

The control module has detected a break in the electrical path of the upstream NOx sensor's internal heater circuit. Because the circuit is open, the heater fails to operate, and the sensor cannot function correctly, which impacts the Selective Catalytic Reduction (SCR) / Diesel Exhaust Fluid (DEF) system's ability to monitor exhaust gases.

• VESTRUM CVX
• Magnum 180
• Magnum 200
• Magnum 220
• Magnum 240
• Magnum 250
• Magnum 280
• Magnum 310
• Magnum 340
• Puma 150
• Puma 150 CVT
• Puma 165
• Puma 165 CVT
• Maxxum
• Steiger
• Combine 5140
• Combine 6140
• Combine 7140
• Combine 7240
• Combine 8240
• Combine 9240
• Patriot 2250
• Patriot 3240
• Patriot 3340
• Patriot 4440
• Titan 3040
• Titan 3540
• Titan 4040
• Titan 4540

1. 1

   Inspect the wiring harness and the connector leading to the upstream NOx sensor for chafing, melted wires, breaks, or severe corrosion.

2. 2

   Check the power supply and ground at the sensor harness connector to ensure the ECU is sending the correct voltage to the heater circuit.

3. 3

   Use a multimeter to measure the resistance across the heater pins on the sensor itself. If the multimeter reads infinite resistance (OL), the internal heater is broken (open circuit), confirming the sensor has failed internally and must be replaced.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical spikes during the repair.

2. 2

   Locate the Sensor

   Locate the upstream NOx sensor. It is threaded into the exhaust pipe before the SCR catalyst and DEF dosing injector.

3. 3

   Disconnect

   Unplug the electrical connector linking the NOx sensor to the machine's wiring harness.

4. 4

   Remove the Sensor

   Using a specialized NOx sensor socket or a wrench, carefully unscrew the sensor from the exhaust pipe. (Note: Penetrating oil may be required if the sensor is seized from exhaust heat).

5. 5

   Install the New Sensor

   Apply a 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 and tighten to the manufacturer's specified torque.

6. 6

   Reconnect

   Route the sensor wiring carefully to ensure it does not rest against extreme heat sources, then plug in the electrical connector.

7. 7

   Clear Codes

   Reconnect the battery, turn the ignition on, and use a Case IH-compatible diagnostic scan tool to clear the 19051 fault code.

8. 8

   Test

   Start the engine and let it reach normal operating temperature to verify the code does not return.