Case IH 19019 (F-4360-03) - ECU – DCU (Dosing Control Unit) / Engine ECU: Upstream SCR catalyst temperature sensor voltage is higher than expected

The signal voltage from the temperature sensor located before the Selective Catalytic Reduction (SCR) catalyst is exceeding the maximum threshold, indicating an open circuit (a broken wire or failed sensor internally) or a short to power in the sensor's wiring harness.

• VESTRUM CVX
• Case IH Magnum 235–340 (Series 4)
• Case IH STX Steiger tractors (350–600 HP)
• Case IH Farmall 40, 45, and 50
• Case IH Puma Series
• Case IH 240 Series Axial-Flow Combines

1. 1

   Visually inspect the upstream SCR catalyst temperature sensor (located just before the catalyst or after the DOC).

2. 2

   Disconnect the sensor and inspect the connector pins for pushed-back pins, bent terminals, corrosion, or moisture intrusion.

3. 3

   Trace the wiring harness from the sensor back to the DCU/ECU. Look for chafed wires, melted insulation from exhaust heat, or pinch points. Test the circuit for continuity and ensure there is no short to a 12V/5V power source.

4. 4

   Measure the resistance across the sensor's terminals with a multimeter. If the sensor reads as an open circuit (infinite resistance), the sensor has failed internally.

1. 1

   Cool exhaust system

   Turn off the machine, remove the key, and allow the exhaust system to cool completely to avoid burns.

2. 2

   Disconnect sensor

   Disconnect the electrical connector from the upstream SCR catalyst temperature sensor.

3. 3

   Repair wiring

   If the diagnostic checks revealed wiring damage, repair the harness or replace the affected pigtail connector.

4. 4

   Remove faulty sensor

   If the sensor itself is faulty (open circuit), use a wrench to carefully unscrew the sensor from the exhaust pipe. (Penetrating oil may be required if the sensor is seized from exhaust heat).

5. 5

   Prepare new sensor

   Apply a small amount of anti-seize compound to the threads of the new sensor (if not already pre-applied by the manufacturer), being careful not to get any on the sensor probe.

6. 6

   Install new sensor

   Thread the new sensor into the exhaust pipe and tighten to the OEM torque specification.

7. 7

   Reconnect harness

   Reconnect the electrical harness, ensuring the weather seal is intact and the connector clicks securely into place.

8. 8

   Clear codes and verify

   Connect a diagnostic tool to clear the inactive fault codes, then start the engine and allow it to reach operating temperature to verify the code does not return.