Case IH 19869 – Engine Control Unit (ECU) or Heater Control Unit (HCU) / Dosing Control Unit (DCU): Over Temperature error of DEF/AdBlue Pressure Line Heater Actuator powerstage

The internal driver circuit (power stage) inside the control module that supplies electrical current to the DEF (Diesel Exhaust Fluid) pressure line heater has overheated. This is typically caused by an excessive current draw, pointing to a short circuit within the DEF pressure line heater element itself, or a short in the wiring harness leading to the heater.

• Tier 4b
• Case IH Axial-Flow Combines (240 Series, 5130)
• Case IH Tractors (Magnum, Steiger, Optum, Puma, Farmall series)
• Case Construction Equipment (N-Series Backhoe Loaders)

1. 1

   Check for related circuit codes such as 19870, 19253, or 19255.

2. 2

   Verify system battery voltage to ensure power stage diagnostics are not disabled or triggered erroneously.

3. 3

   Visually inspect the wiring harness from the ECU/HCU to the DEF pressure line heater for chafing, melted insulation, or pinched wires that could cause a short to ground.

4. 4

   Disconnect the DEF pressure line heater connector and use a multimeter to measure the resistance across the heater pins. A reading near zero indicates the heater element has failed internally.

1. 1

   Power Down

   Turn off the machine and disconnect the battery to prevent any further thermal damage to the ECU/HCU power stage.

2. 2

   Locate the Component

   Locate the DEF/AdBlue pressure line running from the DEF supply module (pump) to the DEF dosing injector on the exhaust.

3. 3

   Disconnect

   Disconnect the electrical connector for the pressure line heater and disconnect the fluid fittings at both ends of the line. Be prepared to catch a small amount of spilled DEF.

4. 4

   Replace the Line

   Remove the faulty line and route the new DEF pressure line carefully. Ensure it is secured away from extreme exhaust heat sources and pinch points.

5. 5

   Reconnect

   Reconnect the fluid fittings and the electrical connector. Reconnect the machine's battery.

6. 6

   Clear Codes and Reset Inducement

   Connect the Case IH Electronic Service Tool (EST) or PT-Box. Clear the inactive fault codes and perform an 'Inducement Unlock / Counter Reset' via the service tool to restore full engine power.