Case IH 19086 (F-4354-14) - ECU – Engine Control Unit (ECU): DEF/AdBlue pressure line heater failure and DEF/AdBlue tank temperature is too low

The system has detected that the DEF (Diesel Exhaust Fluid) tank temperature has dropped below acceptable limits (risking fluid freezing or crystallization), and the heater circuit integrated into the DEF pressure line has failed, shorted, or opened, preventing the system from thawing the fluid.

• VESTRUM CVX
• Magnum
• Steiger
• Puma
• Maxxum
• Farmall 40-45-50
• Farmall 115U
• Axial-Flow 240 series
• Axial-Flow 7230
• Axial-Flow 8230
• Axial-Flow 5130

1. 1

   Visual Inspection: Check the DEF pressure line heater wiring harness and connectors for physical damage, corrosion, or loose pins.

2. 2

   Grounds: Check for any damaged or loose machine earths (grounds) and connector pins, as well as debris or water inside the connector terminals (often caused by pressure washing).

3. 3

   Relay Testing: Test the DEF pressure line heater relays. The system monitors both the low side (line relay) and high side (main heater relay) for open circuits or short circuits to ground/battery.

4. 4

   Sensor Verification: Test the DEF tank temperature sensor (often integrated into the DEF tank header unit) for implausible values, open circuits, or voltage irregularities.

1. 1

   Safety First

   Stop the engine and let the exhaust and aftertreatment system cool completely before starting work. Do not start the engine during the service procedures.

2. 2

   Isolate the Fault

   Use a breakout harness (e.g., Navistar/CNH 18-047-01 DEF Pressure Line Heater Breakout Harness or 18-124-01 DEF Tank Level & Temp Sensor Breakout Harness) to test the circuits without damaging the pins.

3. 3

   Repair Wiring

   If the diagnostic checks reveal a short or open circuit in the harness, repair the wiring or replace the damaged connector.

4. 4

   Replace the Line

   If the harness and relays test good but the heater circuit is still open/shorted, the heating element inside the DEF pressure line has failed. The DEF pressure line must be replaced as an entire assembly, as the heater is integrated into the hose.

5. 5

   Address the Tank Sensor

   If the DEF tank temperature remains implausible after fixing the heater, drain the DEF tank and replace the DEF tank temperature sensor/header unit.

6. 6

   Clear Codes

   Reconnect all components, turn on the key, and use a diagnostic scan tool to clear the fault codes. Run the machine to verify the system builds pressure and the heater operates without throwing the code again.