Case IH 19255 – Heater Control Unit (HCU) or Dosing Control Unit (DCU) / Engine Control Unit (ECU): Open Load error of DEF/AdBlue Pressure Line Heater Actuator powerstage

The control module has detected an 'open load' (an open electrical circuit) in the heating element or the wiring for the Diesel Exhaust Fluid (DEF) pressure line.

• Tier 4b
• Magnum
• Puma
• Maxxum
• Farmall
• loaders
• excavators

1. 1

   Stop the engine and let it cool, waiting 2–5 minutes for the DEF system to complete its automatic purge cycle before disconnecting lines

2. 2

   Inspect the wiring harness and connectors leading to the DEF pressure line heater for physical damage, chafing, or loose pins

3. 3

   Check for damaged or loose machine grounds, and verify the condition of the DEF pressure line heater relay and associated fuses

4. 4

   Disconnect the electrical connector at the DEF pressure line and measure resistance (Ohms) across the heater pins; infinite resistance (OL) indicates a broken heating element

5. 5

   Check the harness side of the connector for proper voltage from the HCU/ECU when the system commands the heater on

1. 1

   Prepare machine

   Ensure the machine is off, the battery is disconnected, and the DEF system has fully purged and depressurized.

2. 2

   Disconnect electrical connector

   Disconnect the electrical connector for the DEF pressure line heater.

3. 3

   Disconnect fittings

   Disconnect the quick-connect SAE J2044 fittings at both ends of the DEF pressure line (one end at the DEF supply module/pump, the other at the dosing module).

4. 4

   Remove faulty line

   Remove the faulty DEF pressure line from its routing clips.

5. 5

   Install new line

   Install the new DEF pressure line. Ensure the quick-connect fittings click securely into place and that the line is not kinked.

6. 6

   Reconnect electrical connector

   Reconnect the electrical connector for the heater.

7. 7

   Clear fault code

   Reconnect the battery, turn the key ON, and use the Case IH EST (Electronic Service Tool) or equivalent diagnostic scanner to clear the fault code.

8. 8

   Verify repair

   Run a system test or start the engine to verify that the code does not return and that there are no DEF leaks.