Case IH F-3224-05 - ECU – Engine Control Unit (ECU) / Engine Management System (EMS): Upstream NOx sensor internal failure (Open Circuit Error)

The system has detected an electrical open circuit or plausibility error within the sensor's internal heater circuit. An open circuit means there is a break in the wiring, a disconnected plug, or the internal heating element of the sensor has burned out.

• MAGNUM AFS Connect
• Magnum (180 to 370)
• Steiger / Quadtrac (350 to 600)
• Puma (130 to 230)
• Maxxum (110 to 140)
• Axial-Flow (5130 to 9230)
• Austoft 9900
• Titan (3030 to 4530)
• Farmlift series

1. 1

   Inspect the wiring harness and the 5-pin MCON connector (Connector C186) leading to the upstream NOx sensor for chafing, melting, or disconnected wires.

2. 2

   Check the sensor's power supply (12V or 24V, depending on the machine) and ground circuits.

3. 3

   Verify the integrity of the CAN communication lines to the sensor.

4. 4

   Measure the resistance of the sensor's internal heater circuit. An infinite resistance reading confirms the open circuit is internal to the sensor, necessitating replacement.

1. 1

   Preparation

   Turn off the engine and allow the exhaust system to cool completely, as the sensor is located in the high-heat exhaust stream before the DOC. Turn off the battery disconnect switch.

2. 2

   Disconnection

   Locate the upstream NOx sensor. Disconnect the 5-pin electrical connector from the main engine harness.

3. 3

   Removal

   Use a specialized NOx sensor socket to carefully unscrew the sensor from the exhaust pipe boss.

4. 4

   Installation

   Apply a small amount of high-temperature anti-seize to the threads of the new sensor (if not pre-applied by the manufacturer), ensuring no paste touches the sensor probe. Thread the new sensor into the exhaust pipe and tighten to the manufacturer's torque specification.

5. 5

   Reconnection

   Reconnect the 5-pin electrical plug and secure the wiring harness away from extreme heat sources.

6. 6

   System Reset

   Turn on the battery. Use the Case IH Electronic Service Tool (EST) to clear the inactive fault codes (including F-3224-05). A single error clearing via the on-board diagnostic tool is required after fitting the new sensor to restore normal operation.