Case IH 19079 (F-4334-15) – Engine ECU or DCU: DEF/AdBlue over pressure failure

The system has detected that the pressure of the Diesel Exhaust Fluid (DEF / AdBlue) within the supply lines or the dosing module is higher than the expected operational threshold. This typically indicates a physical blockage in the fluid delivery/return system, a clogged injector, or a malfunctioning pressure sensor within the pump.

• VESTRUM CVX
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• AUSTOFT 9900 Sugarcane Harvesters
• Magnum
• Maxxum
• Puma
• Steiger
• Patriot series (4430)

1. 1

   Check for Line Blockages: Inspect the DEF pressure line (from the pump to the doser) and the DEF return line for kinks, crushing, or blockages. A blocked return line is a primary cause of over-pressurization.

2. 2

   Inspect the DEF Dosing Valve (Injector): Remove the doser from the SCR exhaust pipe. Check the nozzle for severe crystallization (white urea crust) which can block fluid flow and spike line pressure.

3. 3

   Check the DEF Filter: A heavily contaminated or collapsed DEF supply module filter can cause erratic pressure regulation.

4. 4

   Sensor Verification: Using a diagnostic scan tool, monitor the DEF pressure sensor voltage. If the sensor is reading high pressure even when the machine is off and the lines are disconnected, the internal pressure sensor has failed.

1. 1

   Safely Depressurize

   Turn off the machine and wait for the DEF system to complete its automatic purge cycle (listen for the pump to stop running). This pulls fluid back into the tank and relieves line pressure. Disconnect the battery.

2. 2

   Clean the Dosing Valve

   If the dosing valve is caked in crystallized DEF, clean it using only warm distilled water. Do not use harsh chemicals or wire brushes that could damage the precision nozzle.

3. 3

   Flush the Lines

   Disconnect the DEF lines and blow low-pressure compressed air through them to ensure they are completely clear of blockages.

4. 4

   Replace the DEF Filter

   Clean the area around the DEF supply module filter cap to prevent dirt or dried urea from falling into the reservoir. Use the specialized extraction tool to remove the old filter element without scratching the inner walls of the pump housing. Install a new filter.

5. 5

   Replace the Supply Module

   If the lines and doser are clear, the internal pressure regulator or pressure sensor inside the DEF pump has failed. The Bosch Denoxtronic supply module must be replaced as an assembly.

6. 6

   Relearn/Test

   After replacing components, clear the fault codes using a diagnostic scan tool. Because this fault causes an engine derate/inducement, you must run the 'SCR Fault Repair Verification Test' (or DEF dosing test) via the diagnostic tool to validate the repair and restore full engine power.