Case IH 19860 – Engine Control Unit (ECU): Signal error for CAN message downstream temperature sensor

Communication failure on the Controller Area Network (CAN) bus regarding the exhaust gas temperature sensor located downstream of the Selective Catalytic Reduction (SCR) catalyst. The control module is either receiving a corrupted signal, an out-of-range value, or no signal at all from this specific sensor, which is critical for monitoring the SCR dosing and healing (regeneration) processes.

• Tier 4b
• Farmall 110A-140A
• Farmall 100C-115C
• Farmall 105U-120U
• Maxxum 120-150
• Puma 130-240
• Optum 270-300
• Steiger 350-620
• Quadtrac 350-620
• Rowtrac 350-620
• Axial-Flow 5130-9250
• Axial-Flow 6140
• Axial-Flow 8250
• Case Wheel Loader 621F
• Case Wheel Loader 921G
• Case Wheel Loader 1021G

1. 1

   Inspect the wiring harness and connector at the SCR downstream temperature sensor for physical damage, melted wires, corrosion, or pushed-out pins.

2. 2

   Check the CAN High and CAN Low lines between the sensor and the ECU for continuity, shorts to ground, or shorts to battery.

3. 3

   Verify that the sensor module is receiving proper supply voltage and has a solid ground connection.

4. 4

   Use the CNH Electronic Service Tool (EST) to check for other CAN communication codes. If multiple sensors are dropping off the network simultaneously, the issue is likely a damaged CAN backbone rather than the sensor itself.

1. 1

   Turn off the machine, remove the key, and disconnect the battery to protect the electrical system.

2. 2

   Locate the SCR downstream temperature sensor.

   It is threaded into the exhaust pipe immediately after the SCR catalyst/muffler.

3. 3

   Disconnect the sensor's electrical connector.

4. 4

   If necessary for access, remove the retaining bolts and take off the SCR muffler/catalyst lower cover and heat shields.

5. 5

   Unscrew the downstream temperature sensor from the exhaust pipe.

6. 6

   Apply a high-temperature anti-seize compound to the threads of the new sensor (if it does not come pre-applied).

7. 7

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

8. 8

   Reconnect the electrical connector, ensuring it clicks securely into place.

9. 9

   Reinstall any heat shields or covers that were removed.

10. 10

    Reconnect the battery.

11. 11

    Connect the CNH EST diagnostic tool, clear the inactive 19860 fault code, and run an SCR system healing procedure (forced regeneration/dosing test).

    Verify that the ECU is reading the downstream temperature correctly and the system reaches the required 220 - 240 °C (428.0 - 464.0 °F).