Case IH 19550 – DCU (Dosing Control Unit): Pressure line blocked / Reagent dosing nozzle pressure too high / Discharge line obstruction

The system has detected that the Diesel Exhaust Fluid (DEF / AdBlue) pressure in the supply line is too high. This typically indicates a physical blockage in the DEF pressure line or a clogged dosing nozzle (injector) preventing the fluid from being sprayed into the exhaust stream. It can also be triggered by a failed DEF pump/dosing module.

• Tier 4b
• Magnum Tractors (235, 250, 280, 310, 340, 380)
• Steiger / Quadtrac Tractors (350, 370, 400, 420, 450, 470, 500, 540, 580, 620)
• Puma Tractors (150, 165, 185, 200, 220)
• Farmall Tractors (90C, 95A)
• Axial-Flow Combines (7230, 8230, 7240, 8240, 7250, 8250)

1. 1

   Inspect the Dosing Nozzle (Injector) for crystallized DEF on the tip, which is the most common cause of blockage.

2. 2

   Check the DEF supply line between the pump and the dosing unit for kinks, crushed sections, or internal crystallization.

3. 3

   Test the Dosing Valve Circuit using an Electronic Service Tool (EST) to run a system test. Check if the dosing valve clicks or attempts to actuate, and verify the wiring harness for shorts or open circuits.

4. 4

   Inspect the DEF filter inside the pump module for heavy contamination or collapse, which can cause pressure irregularities.

5. 5

   Check DEF quality to ensure the tank is free of dirt, dust, or chemical contamination that accelerates crystallization.

1. 1

   Clean the Dosing Nozzle

   If the nozzle is clogged with crystallized DEF, soak the tip in warm/hot distilled water. Alternatively, use pressurized water and an injector pulser to clear the blockage and verify the spray pattern.

2. 2

   Flush the Supply Line

   Disconnect the AdBlue supply line at the dosing unit and plug it off. Disconnect the pressure side line at the supply module. Use a bulge pump and warm water to flush the line and dissolve any crystallized deposits.

3. 3

   Replace the DEF Filter

   Replace the DEF filter (typically a 70-micron filter) during this service to prevent future pressure issues.

4. 4

   Replace the Dosing Module

   If cleaning the nozzle and lines does not resolve the pressure issue, or if the pump motor is internally damaged/unresponsive to the EST system test, the entire DEF Dosing Module (pump) must be replaced.

5. 5

   Reassemble and Clear Codes

   Reconnect all lines, install the new filter/pump if applicable, clear the DCU codes using a diagnostic tool, and run a forced DEF dosing test to ensure pressure is within normal limits.