Case IH 19150 – DCU (Dosing Control Unit): Dosing Valve (electrical) – Dosing valve permanent "ON" (detection via fast decay) / Reagent - dosing nozzle - pressure too high.

The system has detected that the Diesel Exhaust Fluid (DEF / AdBlue) dosing valve is stuck in the open ("ON") position, or there is a blockage in the pressure line. Because the valve is not cycling properly or the line is obstructed, the system detects abnormally high pressure at the dosing nozzle.

• Tier 4a
• Magnum Series (235, 250, 280, 290, 340 Series 4)
• Steiger Series (350, 400, 450)
• Puma Series
• Maxxum Series

1. 1

   Inspect the dosing injector tip and mixing chamber for white scale deposits (crystallized DEF) that can block the nozzle

2. 2

   Test the DEF fluid concentration to ensure it is exactly 32.5% automotive-grade urea and 67.5% distilled water

3. 3

   Inspect the exhaust pipe and SCR catalyst housing for physical damage, cracks, or leaks

4. 4

   Check the DEF supply and return pressure lines to ensure they are not pinched, kinked, or blocked

1. 1

   Clean the Injector and Chamber

   If scale build-up is found on the dosing injector tip or inside the mixing chamber, clean it thoroughly. Crystallization is especially common if the tractor has been sitting unused for extended periods.

2. 2

   Replace DEF Fluid (If Necessary)

   If the DEF concentration test fails, drain the DEF tank completely, flush it, and refill it with fresh, high-quality DEF.

3. 3

   Replace the Dosing Valve

   If the injector tip is clean, the lines are clear, and the DEF quality is correct, the dosing valve has suffered an internal mechanical or electrical failure (stuck open). Disconnect the electrical harness connector. Squeeze the locking tabs together and pull straight upward to disconnect the DEF supply and return hoses. Cap all open fittings immediately. Unbolt and remove the failed dosing valve. Install the new dosing valve using new O-rings (discard the old ones). Reconnect the DEF lines and electrical harness.

4. 4

   Clear Codes and Test

   Use an Electronic Service Tool to clear the fault codes from the DCU and ECU. Run the machine to verify the system is operating properly and that the pressure has normalized.