Case IH 19156 – DCU (Dosing Control Unit): DEF/AdBlue supply module pump motor severe speed deviation

The electric motor inside the DEF supply pump is running at a much higher RPM than commanded. This typically happens when the pump loses its fluid prime and is spinning freely with no resistance (e.g., drawing air due to an empty tank, a severe leak, a blocked pickup tube, or an internal pump failure).

• Tier 4a
• Tier 4b
• Steiger (350, 400, 450, 500, 550, 600)
• Quadtrac (350, 400, 450, 500, 550, 600)
• Magnum (235-340 Series 4)
• Puma series
• 240 Series Axial-Flow Combines (e.g., 8230)
• Titan Floaters (3530, 4030)

1. 1

   Verify if the fault is currently active. If inactive, clear it and run the machine to see if it returns.

2. 2

   Check DEF tank fluid level to ensure it is not empty, which causes the pump to suck air and overspeed.

3. 3

   Verify DEF/AdBlue concentration is correct and the fluid is not contaminated.

4. 4

   Inspect DEF supply lines between the tank, supply module, and dosing injector for leaks, cracks, or disconnected fittings.

5. 5

   Check the exhaust pipe for damage or cracks near the dosing injector.

1. 1

   Remove the Dosing Injector

   Unbolt the DEF dosing injector from the exhaust pipe.

2. 2

   Inspect the Injector

   Check the injector nozzle for severe crystallization, blockage, or mechanical failure. Clean or replace the injector if it has failed.

3. 3

   Test the Supply Module

   If the injector and lines are intact, the fault lies within the DEF/AdBlue Supply Module (the pump itself). The internal motor or pressure regulation system has failed.

4. 4

   Replace the DEF Supply Module

   Remove the defective pump module, install the replacement, and reconnect the fluid lines and electrical harnesses.

5. 5

   Prime and Clear

   Turn the key on to allow the system to prime. Use the Case IH Electronic Service Tool (EST) or the in-cab diagnostic menu to clear the fault code and run a stationary regen/dosing test to verify the repair.