Case IH 19541 – DCU (Dosing Control Unit): DEF/AdBlue pressure did not drop when the dosing valve was open

When the DeNOx supply module performs a system test, it fully opens the dosing valve and checks the pressure. If the pressure does not drop below the expected threshold (typically 30 kPa / 4.35 psi), the system detects that the backflow/pressure line is clogged, or that the supply module itself has failed to vent the pressure.

• Tier 4b
• Steiger & Rowtrac Series 350
• Steiger & Rowtrac Series 400
• Steiger & Rowtrac Series 450
• Steiger & Rowtrac Series 500
• Steiger & Rowtrac Series 550
• Steiger & Rowtrac Series 600
• Magnum Series 180
• Magnum Series 200
• Magnum Series 220
• Magnum Series 240
• Magnum Series 250
• Magnum Series 280
• Magnum Series 310
• Magnum Series 340
• Magnum Series 380
• Puma Series 140
• Puma Series 150
• Puma Series 165
• Puma Series 185
• Puma Series 200
• Puma Series 220
• Puma Series 240
• Maxxum Series 115
• Maxxum Series 125
• Maxxum Series 135
• Maxxum Series 145
• Maxxum Series 150
• Optum Series 270
• Optum Series 300
• Case Construction Wheel Loader 521G2
• Case Construction Wheel Loader 821F
• Case Construction Wheel Loader 921F

1. 1

   Verify that the DEF pressure line and backflow return lines are not frozen, crimped, collapsed, or clogged

2. 2

   Remove the DEF dosing injector and inspect the tip and the mixing chamber for white scale (urea crystallization) build-up

3. 3

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

4. 4

   Ensure the wiring harness is properly connected to the coolant control valve and the dosing valve, checking for open or short circuits

5. 5

   Ensure the exhaust pipe is not damaged or cracked near the dosing module

1. 1

   Clear Blockages

   If the pressure or backflow lines are clogged or frozen, safely thaw or clear the lines so they are completely free-flowing.

2. 2

   Clean the Dosing Injector

   If scale build-up is present on the dosing injector tip, clean it thoroughly with warm distilled water to ensure vaporized DEF can mix properly.

3. 3

   Replace Fluid

   If the DEF concentration is incorrect or contaminated, drain the tank entirely and refill it with fresh, correct-spec DEF.

4. 4

   Replace the Supply Module / Valve

   If all lines are open, the wiring is intact, and the system is mechanically sound but the fault persists, the DeNOx supply module (DEF pump) has internally failed and must be replaced.

5. 5

   System Relearn/Validation

   Bring the engine to normal operating temperature and run the machine under load for up to 30 minutes. The code will only clear once the SCR system runs its self-check and determines it is operating properly.