Case IH 19818 – DCU (Dosing Control Unit): Plausibility of UDV stuck - P202D Dynamic urea leakage test - leakage detected.

The system has detected that the Urea Dosing Valve (UDV) / DEF Injector is stuck in the open position or is leaking. The system runs a dynamic urea leakage test by pressurizing the DEF lines and monitoring for unexpected pressure drops when the valve is commanded closed. A pressure drop indicates the valve is mechanically stuck open, fouled by crystallized DEF, or electrically shorted open.

• Tier 4a
• Tier 4B
• Steiger 350
• Steiger 400
• Steiger 450
• Steiger 500
• Steiger 550
• Steiger 600
• Magnum 235-340
• Puma series
• Farmall models
• Axial-Flow 6130
• Axial-Flow 6140
• Axial-Flow 7230
• Axial-Flow 8230
• Patriot 4430

1. 1

   Visually inspect the DEF lines running from the supply pump to the dosing valve on the exhaust pipe for external leaks, cracked lines, or loose fittings.

2. 2

   Inspect the wiring harness and connector at the UDV for a short to ground, which could cause the valve to be continuously energized.

3. 3

   Remove the DEF injector from the exhaust pipe and inspect for severe DEF crystallization (white buildup) on the nozzle that might be physically wedging the pintle open.

4. 4

   Using the CNH Electronic Service Tool (EST), run a manual DEF system pressure test to see if the nozzle drips or sprays fluid while commanded closed under pressure.

1. 1

   Depressurize the System

   Turn off the machine and wait at least 5–10 minutes for the DEF system to automatically purge and depressurize. Do not disconnect lines immediately after shutdown.

2. 2

   Disconnect the Valve

   Locate the Urea Dosing Valve on the SCR mixing pipe (exhaust). Disconnect the electrical harness connector and the DEF fluid supply line. Note: Have a rag ready, as a small amount of DEF may spill.

3. 3

   Remove the Valve

   Remove the V-band clamp or mounting bolts securing the dosing valve to the exhaust pipe boss.

4. 4

   Clean the Mounting Boss

   Carefully scrape away any crystallized DEF or carbon buildup from the mounting port on the exhaust pipe to ensure the new injector seats properly.

5. 5

   Install the New Valve

   Seat the new DEF injector into the port and tighten the clamp/bolts to OEM torque specs.

6. 6

   Reconnect

   Reattach the DEF supply line and plug in the electrical connector.

7. 7

   Prime and Clear Codes

   Turn the key to the ON position. Use the CNH EST laptop to clear the 19818 / P202D fault codes. Run a system prime command or dynamic leak test via the software to verify the leak is resolved and the system builds/holds pressure.