Case IH 19051 – Engine Control Unit (ECU) / Engine Management System (EMS): Upstream NOx sensor internal failure (Heater Open Circuit Error)

The upstream Nitrogen Oxide (NOx) sensor's internal heating element has suffered an open circuit, preventing the sensor from reaching the high temperatures required to accurately measure NOx levels.

• Tier 4b
• Tier 4B and Stage V equipment
• Farmall (110A-140A)
• Magnum (180-380)
• Maxxum (115-150)
• Puma (150-220)
• Steiger 4WD & Quadtrac (370-620)
• Optum (250-300)
• 140 and 240 Series Axial-Flow Combines (5140, 6140, 7140, 7240, 8240, 9240)
• Patriot Sprayers (2250, 3240, 3340, 4440)
• Bale Wagons (102, 103, 105)

1. 1

   Locate the upstream NOx sensor before the DOC and visually inspect the sensor body and its wiring harness for physical damage, melting, or chafing.

2. 2

   Inspect the 5-pin electrical connector (Connector C186) for the upstream NOx sensor. Look for corrosion, backed-out pins, or moisture intrusion that could cause an open circuit.

3. 3

   Check the ECU for other related NOx sensor codes (such as 19052 Heater Short Circuit, 19054 Open Circuit Error, or 19060 CAN timeout). If multiple codes are present, the issue may be a damaged main wiring harness rather than the sensor itself.

1. 1

   Preparation

   Turn off the engine and allow the exhaust system to cool completely to avoid severe burns.

2. 2

   Disconnection

   Locate the upstream NOx sensor in the exhaust pipe before the DOC. Disconnect the 5-pin electrical connector (C186) from the machine's wiring harness.

3. 3

   Removal

   Use a specialized NOx/O2 sensor socket or wrench to carefully unscrew the faulty NOx sensor from the exhaust pipe.

4. 4

   Installation

   Thread the new NOx sensor into the exhaust pipe and tighten it to the manufacturer's specified torque.

5. 5

   Reconnection

   Plug the 5-pin electrical connector back into the harness, ensuring it clicks securely into place.

6. 6

   Software Reset

   Connect the Case IH Electronic Service Tool (EST) to the machine's diagnostic port. Clear the inactive fault codes. You must then perform the 'Upstream NOx sensor reset (step 1)' and 'Upstream NOx sensor reset (step 2)' via the diagnostic tool to calibrate the new sensor to the ECU.