Case IH 19195 – Engine ECU (DCU - Dosing Control Unit / SCR Control Unit) or VCM (Vehicle Control Module): Signal range check: high error when heater is Off

This fault code indicates a plausibility error within the Diesel Exhaust Fluid (DEF) / AdBlue heating system. The system detects an out-of-range high signal (either a high temperature reading or a high voltage signal) on the DEF heater circuit when the Engine Control Unit has commanded the heater to be OFF. This is most commonly caused by a DEF tank heater control valve intermittently sticking open, allowing hot engine coolant to continuously circulate and overheat the fluid.

• Tier 4b
• Steiger
• Magnum
• Puma
• Maxxum
• N-Series Tractor Loader Backhoes (TLBs)
• T7
• T8
• T9

1. 1

   Inspect the DEF Heater Control Valve (coolant valve) to see if it is intermittently sticking open.

2. 2

   Verify coolant hose routing to the DEF heater (valves are directional; on Fargo-built tractors, the red band line must connect to the top tube running to the front of the engine head).

3. 3

   Test the DEF tank temperature sensor using the CNH Electronic Service Tool (EST) on a cold soak to see if it reads artificially high.

4. 4

   Inspect the wiring harness connecting the DEF heater control valve and the DEF sender unit for chafing or shorts to voltage.

1. 1

   Connect Diagnostic Tool

   Hook up the CNH EST to verify active fault codes and monitor live data for the DEF tank temperature and Heater Control Valve status.

2. 2

   Perform Valve Leak/Function Test

   Command the DEF heater control valve closed. Carefully feel the coolant return line from the DEF tank. If it remains hot, coolant is bypassing the valve.

3. 3

   Correct Hose Routing

   If the hoses are reversed, drain the coolant, swap the hoses to their correct directional orientation, and refill/bleed the coolant system.

4. 4

   Replace the Heater Control Valve

   If the valve is correctly plumbed but stuck open or leaking internally, drain the engine coolant, remove the faulty DEF heater control valve, install the replacement valve, and refill the coolant.

5. 5

   Replace the DEF Sender Unit

   If the valve is functioning perfectly but the temperature sensor is reading out of range, replace the DEF tank sender unit assembly (which houses the level and temperature sensors).

6. 6

   Clear Codes

   Cycle the key, clear the fault code 19195 via the EST, and run the machine to ensure the DEF temperature remains stable and the code does not return.