Case IH 19870 – Engine Control Unit (ECU) or Dosing Control Unit (DCU): Short Circuit to Ground of DEF/AdBlue Pressure Line Heater Actuator powerstage

The control module has detected a short to ground in the electrical circuit (the "powerstage" or driver circuit) that supplies power to the heating element inside the DEF pressure line. This is typically caused by chafed wiring touching the machine's frame, a melted connector, or an internal failure of the heating element itself.

• Tier 4b
• Magnum
• Steiger
• Puma
• Maxxum
• Optum
• Axial-Flow series
• 850M
• 1150M
• 1650M
• 2050M

1. 1

   Visually inspect the DEF pressure line and wiring harness for chafing against the chassis, engine block, or moving parts.

2. 2

   Disconnect the DEF pressure line heater electrical connector and inspect pins for corrosion, water intrusion, or melting.

3. 3

   Measure the resistance of the heater circuit on the DEF line side of the connector (a healthy element reads around 5.5 ohms at 68°F; zero indicates an internal short).

4. 4

   Test the machine-side harness with the key ON to ensure the ECU/DCU is sending the correct voltage and the short is not in the main wiring harness.

1. 1

   Power Down

   Turn off the machine and disconnect the battery to prevent electrical spikes or accidental DEF dosing.

2. 2

   Access the Line

   Locate the DEF pressure line. Note its exact routing, as improper routing of the new line can lead to premature failure from heat or abrasion.

3. 3

   Disconnect Fittings

   Disconnect the electrical connector for the heater. Then, disconnect the fluid fittings at the DEF pump and the DEF doser. Note: DEF crystallizes when exposed to air; clean any spills immediately with warm water.

4. 4

   Remove the Line

   Unclip the retaining clips or zip ties holding the line to the frame bracket and remove the faulty DEF pressure line.

5. 5

   Install the New Line

   Route the new heated DEF line exactly as the original. Ensure it is secured with clips and is kept away from sharp edges and the hot exhaust manifold.

6. 6

   Reconnect

   Snap the quick-disconnect fluid fittings into place and plug in the electrical connector.

7. 7

   Clear Codes and Test

   Reconnect the battery. Use the CNH Electronic Service Tool (EST) or the machine's diagnostic display to clear the inactive fault code 19870. Start the engine and run a DEF system leak test or heater test to verify the repair.