Case IH 19541 (F-4334-14) – DCU (Dosing Control Unit) or Engine ECU: DEF Dosing Valve Blockage or Coolant Control Valve Blocked Closed

The system commanded the DEF dosing valve to open, but the pressure sensor in the DEF line did not detect the expected pressure drop, indicating a blockage, clogged line, or faulty sensor. Alternatively, on some platforms, it indicates the DEF tank heater coolant control valve is mechanically blocked closed (P20A1).

• VESTRUM CVX
• Case IH Farmall (40-50 CVT, 110A-140A)
• Case IH Magnum (235–340 Series 4)
• Case IH Steiger / Quadtrac (350–600)
• Case IH Puma series

1. 1

   Inspect the DEF dosing valve nozzle for severe urea crystallization (white buildup)

2. 2

   Check the DEF pressure lines between the pump and the dosing valve for kinks, freezing, or blockages

3. 3

   Use an Electronic Service Tool (EST) to perform an active test (UDVC/UDST) to command the dosing valve open and monitor pressure sensor readings

4. 4

   If the P20A1 definition applies (Magnum/Steiger/Puma), check the DEF tank heater coolant control valve to ensure it is not stuck closed by feeling if the coolant lines to the DEF tank are warm

1. 1

   Depressurize the system

   Turn off the machine and disconnect the battery to ensure the DEF pump is not active and the system is depressurized.

2. 2

   Locate the DEF dosing valve

   Locate the DEF dosing valve on the exhaust SCR pipe.

3. 3

   Disconnect the valve

   Carefully disconnect the electrical harness connector and the DEF fluid line from the valve.

4. 4

   Remove the valve

   Unbolt and remove the DEF dosing valve from the exhaust pipe.

5. 5

   Clean the nozzle

   Soak the nozzle in warm distilled water to dissolve crystallized DEF. Do not use harsh chemicals, compressed air, or wire brushes, as this will damage the precision nozzle.

6. 6

   Replace the valve if necessary

   If the blockage cannot be cleared or the valve's internal solenoid has failed, replace the DEF dosing valve.

7. 7

   Reinstall the valve

   Reinstall the cleaned or new valve, torque the mounting bolts to OEM spec, and reconnect the fluid line and electrical harness.

8. 8

   Replace the inline DEF filter

   Replace the inline DEF filter, as debris often causes valve blockages.

9. 9

   Test the system and clear codes

   Reconnect the battery, use a diagnostic tool to run a DEF system leak/dosing test to verify the pressure drops when commanded, and clear the fault codes.