Case IH 19020 (F-4360-04) - ECU – Engine ECU or DCU: Upstream SCR catalyst temperature sensor voltage is lower than expected

The control unit has detected that the voltage signal from the temperature sensor located upstream of the Selective Catalytic Reduction (SCR) catalyst is below the minimum acceptable threshold. Because this is a 5-volt reference circuit, a low voltage signal typically indicates a short circuit to ground, a completely failed sensor (internal short), or a severely damaged wiring harness.

• VESTRUM CVX
• Magnum Series: 180, 200, 220, 235, 240, 250, 280, 310, 340, 380
• Steiger / Quadtrac Series: 350 to 600
• Axial-Flow Combines: 240 Series
• Sugarcane Harvesters: Austoft 9900
• Vestrum Series: 100, 110, 120, 130

1. 1

   Connect the Electronic Service Tool (EST) to determine if the fault is currently active or intermittent.

2. 2

   Inspect the wiring harness leading to the upstream SCR temperature sensor (located on the exhaust pipe before the catalyst/DOC) for melted wires, chafing against the exhaust, or corrosion inside the 2-pin connector.

3. 3

   Disconnect the sensor, turn the key to the ON position, and use a multimeter to verify that Pin 1 on the harness side is receiving a 5V reference signal from the ECU, and Pin 2 has a clean path to ground.

4. 4

   If the 5V reference is missing or pulled down, check the signal wire for continuity to ground (a short to ground in the harness will trigger this specific code).

5. 5

   If the harness tests perfectly, perform a sensor resistance test, as the sensor itself has likely failed internally and is shorting the signal.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical spikes to the DCU/ECU.

2. 2

   Locate the Sensor

   Locate the upstream SCR temperature sensor on the exhaust aftertreatment assembly. It will be threaded into the exhaust piping just before the main SCR catalyst chamber.

3. 3

   Disconnect

   Unplug the 2-pin electrical connector from the sensor.

4. 4

   Remove the Sensor

   Using an appropriately sized wrench or sensor socket, carefully unthread the sensor from the exhaust pipe. (Note: Exhaust sensors are prone to seizing. You may need to apply penetrating oil and allow it to soak before removal to avoid stripping the exhaust bung threads).

5. 5

   Install New Sensor

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if it does not come pre-coated). Thread it into the exhaust bung and tighten to OEM torque specifications.

6. 6

   Reconnect

   Plug the 2-pin harness connector back into the new sensor. Ensure the wiring is routed away from direct contact with the hot exhaust piping.

7. 7

   Clear Codes

   Reconnect the battery. Turn the ignition on and use the EST (Electronic Service Tool) to clear the 19020 / P0427 fault code.

8. 8

   Test Run

   Start the engine and allow it to reach operating temperature. Monitor the exhaust temperature readings via the EST or cab display to ensure the new sensor is broadcasting accurately and the code does not return.