Case IH 19335 (F-5392-14) – DCU (Dosing Control Unit): DEF/AdBlue system unable to build sufficient pressure for dosing

This code indicates that the DEF (Diesel Exhaust Fluid) system failed to build the required pressure to inject fluid into the exhaust stream. In many cases, this is accompanied by OBD code P20BE. The system logs this fault when it detects that the DEF pressure line is frozen and has failed to thaw within the allotted time, preventing the pump from building pressure.

• VESTRUM CVX
• Magnum Tractors 235 - 340 (Series 4)
• Steiger Tractors 350 - 600
• Combines 240 Series (Axial-Flow)
• Farmall Tractors (115U, 40-50 CVT)

1. 1

   Check for freezing/thawing issues: Verify if the machine is operating in freezing temperatures, which indicates the issue is likely the DEF line heater rather than the pump.

2. 2

   Inspect the DEF pressure line heater circuit: Check the actuator power stage for an open circuit, short to ground, or short to battery (high source).

3. 3

   Check harness and connectors: Inspect the wiring harness and connector pins going to the DEF dosing pump and the DEF pressure line heater for corrosion, damage, or loose grounds.

4. 4

   Check battery voltage: Ensure voltage is within normal range. Codes 19361 or 19362 can prevent the ECU from properly diagnosing the output power stages of the DEF heaters.

5. 5

   Inspect for leaks or blockages: Physically inspect the DEF pressure line from the pump to the doser for kinks, blockages, or external leaks that would prevent pressure buildup.

1. 1

   Safety First

   Stop the engine, turn off the battery disconnect, and let the exhaust system cool completely before starting work. Do not start the engine during the service procedure.

2. 2

   Test the Heater Resistance

   Disconnect the DEF pressure line electrical connector. Use a multimeter to test the resistance of the heating element inside the line. If it reads as an open circuit (infinite resistance) or is shorted, the line itself has failed and must be replaced.

3. 3

   Remove the Defective Line

   Disconnect the DEF pressure line from the DEF pump module and the dosing injector. Note: OEM guidelines state that the pressure line uses quick-connect SAE J2044 fittings.

4. 4

   Install the New Pressure Line

   Route the new DEF pressure line exactly as the old one was routed to prevent chafing. Ensure the end caps remain on the new line until the exact moment of installation to prevent dirt ingress. Snap the quick-connect fittings into place.

5. 5

   Reconnect Wiring

   Plug the heater electrical connector back into the harness.

6. 6

   System Prime and Test

   Turn the key on and clear the inactive fault codes. Use the diagnostic service tool to command a DEF system pressure test or dosing test to verify that the system can now build and hold sufficient pressure.