Case IH 19022 – DCU (Dosing Control Unit): Temperature sensor before catalyst (electrical) — signal below low error threshold (or signal low)

The engine control system is receiving a voltage signal from the Exhaust Gas Temperature (EGT) sensor located upstream (before) the Selective Catalytic Reduction (SCR) catalyst that is lower than the acceptable operating range. This typically points to an open circuit, a short to ground in the sensor wiring, or a completely failed sensor element.

• Tier 4a
• Tier 4A and Tier 4B emissions-compliant Case IH equipment
• Puma
• Magnum (e.g., 235-340 Series 4)
• Steiger
• Maxxum
• Optum
• Farmall
• Patriot Sprayers
• compact track loaders (e.g., TR340)

1. 1

   Perform a plausibility check using an Electronic Service Tool (EST) or diagnostic scanner to read live data for 'Temperature before catalyst' on a cold engine; it should match ambient temperature.

2. 2

   Visually inspect the wiring harness leading from the EGT sensor to the DCU for melted wires, chafing, or broken connections.

3. 3

   Perform a continuity/resistance test across the disconnected sensor pins; infinite resistance (OL) confirms a dead sensor.

4. 4

   Test the harness side for proper reference voltage (usually 5V) and ground to ensure the DCU is sending the correct signal.

1. 1

   Preparation

   Ensure the machine is parked on a level surface, the engine is turned off, and the exhaust system has completely cooled down to prevent severe burns.

2. 2

   Locate the Sensor

   Locate the SCR catalyst/muffler assembly. Identify the EGT sensor threaded into the exhaust pipe before the catalyst inlet.

3. 3

   Disconnect Wiring

   Carefully unplug the electrical connector for the sensor. Clean any dirt or debris from around the sensor base to prevent it from falling into the exhaust stream.

4. 4

   Remove the Sensor

   Using a specialized sensor socket or a flare-nut wrench, carefully unthread the sensor. Tip: If the sensor is seized due to heat cycling, apply penetrating oil and allow it to soak before applying torque to avoid stripping the exhaust bung threads.

5. 5

   Install the New Sensor

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if not already pre-applied by the manufacturer). Thread it in by hand to prevent cross-threading, then tighten to OEM torque specifications.

6. 6

   Reconnect and Route

   Reconnect the electrical harness. Ensure the wire is routed away from direct contact with the hot exhaust piping and secured with high-temp zip ties if necessary.

7. 7

   Clear Codes and Test

   Turn the key on, connect the diagnostic tool, and clear the 19022 fault code. Start the engine and monitor the live temperature data to ensure it rises smoothly as the exhaust heats up. (Note: If the code persists after verifying the wiring and replacing the sensor, the official procedure dictates replacing the UREA pump module / DCU).