Case IH 19885 – Heater Control Unit (HCU) / Vehicle Control Module (VCM): DEF/AdBlue tank temperature is too high.

The temperature sensor located inside the Diesel Exhaust Fluid (DEF) tank has detected that the fluid temperature has exceeded the maximum allowable operating threshold.

• Tier 4b
• Case IH Steiger Tractors (400, 450, 500, 550, 600 series)
• Case N-Series Loader Backhoes (TLBs)
• Case Wheel Loaders (621G, 821F, 921F, 1021G)
• Case IH Combines

1. 1

   Check DEF Heater Hose Routing (incorrect routing cause): Inspect the coolant hoses running to the DEF tank. If installed incorrectly during a previous repair, hot engine coolant can circulate continuously and overheat the tank.

2. 2

   Test the DEF Tank Heater Control Valve (sticking valve cause): This valve regulates the flow of hot engine coolant to the DEF tank. It is highly prone to sticking open intermittently, which will constantly heat the tank regardless of ambient temperature.

3. 3

   Verify Sensor Plausibility (failed sensor cause): Use the Case IH Electronic Service Tool (EST) to read the live DEF tank temperature. If the EST reports a dangerously high temperature but the tank is physically cool to the touch, the DEF temperature sensor itself has failed.

1. 1

   Connect EST

   Connect the Case IH EST to the machine's diagnostic port to monitor live DEF temperature data and confirm the 19885 fault is active.

2. 2

   Inspect coolant lines

   Inspect the coolant lines at the DEF tank heater. Ensure the supply and return lines are routed correctly according to your specific model's service manual. Correct them if they are reversed.

3. 3

   Locate valve

   Locate the DEF Tank Heater Control Valve in the coolant line.

4. 4

   Replace valve

   If the hose routing is correct but the fault returns repeatedly, the heater control valve is sticking open. Pinch off or drain the engine coolant to prevent spills, then remove and replace the DEF tank heater control valve.

5. 5

   Replace sensor

   If the valve is functioning properly but the sensor is reporting a false high temperature, replace the DEF Tank Level/Temperature Sensor unit.

6. 6

   Verify repair

   Refill any lost engine coolant, clear the fault codes using the EST, and run the machine to verify the DEF temperature remains within normal operating limits.