Case IH 19871 – Engine Control Unit (ECU) or Aftertreatment Control Module (ACM): Over Temperature of DEF/AdBlue Suction Line Heater Actuator powerstage

The internal driver (power stage) inside the control module that supplies electrical current to the DEF suction line heater is overheating. This condition is typically triggered by an excessive current draw caused by a short circuit in the DEF suction line heater element, a short to ground in the wiring harness, or an internal failure of the control module itself.

• Tier 4b
• Steiger
• Magnum
• Puma
• Optum
• Axial-Flow Combines (6150, 7250)
• Patriot Sprayers (3340)
• N-Series Loader Backhoes
• SV-Series Skid Steers

1. 1

   Visually inspect the DEF suction line (from DEF tank to supply module) and its wiring harness for chafing, melting, or pinched wires that could cause a short to ground.

2. 2

   Disconnect the DEF suction line heater connector and measure the resistance of the heater element using a multimeter (near 0 ohms indicates an internal short).

3. 3

   Check the wiring harness between the ECU/ACM and the DEF suction line heater for continuity and shorts to ground or battery.

4. 4

   Inspect the DEF heater relay for internal shorting or melted pins.

5. 5

   Check the ECU connector pins for signs of thermal damage or corrosion.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the battery to prevent further damage to the ECU.

2. 2

   Access the DEF Tank

   Locate the DEF suction line at the top/side of the DEF tank.

3. 3

   Disconnect

   Unplug the electrical connector for the DEF suction line heater.

4. 4

   Replace the Line (If Shorted)

   If the resistance test confirmed a shorted heater element, the entire DEF suction line must be replaced, as the heating element is integrated into the line. Disconnect the fluid fittings (be careful with the 90-degree retaining ears, as they are prone to breaking) and install the new line.

5. 5

   Repair Wiring (If Applicable)

   If the line tested good but the harness was chafed, repair the damaged section of the wiring harness using OEM-approved weather-sealed connectors.

6. 6

   ECU Replacement (Worst Case)

   If the wiring and heater element are both in perfect condition, the ECU power stage has likely suffered a permanent internal failure and the ECU will need to be replaced and reprogrammed by a dealer.

7. 7

   Reassembly and Testing

   Reconnect the battery. Use the Case IH Electronic Service Tool (EST) to clear the fault codes and run a manual DEF system heater test to verify the repair.