Case IH F-4334-17 - ECU – Engine Control Unit (EDC / Engine ECU) or Denox Module (Denoxtronic ECU): DEF/AdBlue under pressure failure

The DEF/AdBlue supply module pump motor pressure sensor is reading a voltage or pressure that is lower than expected. The system is failing to build or maintain the required pressure (typically around 5 bar / 72 psi) to properly inject diesel exhaust fluid into the SCR system.

• MAGNUM AFS Connect
• Steiger
• Steiger 450
• Magnum
• Magnum 370
• Puma
• Maxxum
• Farmall
• 240 Series Axial-Flow Combines
• 7240
• 8240
• 9240
• Austoft 9900
• CH570

1. 1

   Verify DEF/AdBlue tank fluid level is sufficient and fluid is not contaminated.

2. 2

   Check electrical system and wiring for battery defects, alternator issues, or high resistance causing a voltage drop at the pump motor.

3. 3

   Inspect the WEMA unit (pickup tube) inside the DEF tank for suction issues, vibration damage, or cracks (updated units feature doubled-up O-rings).

4. 4

   Perform a Urea Dosing System Test (UDST) using the Case IH Electronic Service Tool (EST) to confirm system pressure reaches 4900-6200 millibar and pulls a vacuum between -50 and -300 millibar during evacuation.

1. 1

   Command pressure build

   Command the system to build 5 bar of pressure.

2. 2

   Check pressure and replace pump if needed

   If 5 bar is NOT reachable: The pump is not delivering enough fluid, there is a severe internal leakage, or the reverting valve is blocked open. Replace the DEF pump module.

3. 3

   Test dosing valve

   If 5 bar IS reachable: Open the dosing valve fully for approximately 3 seconds. If the pressure drops, replace the DEF pump module. If the pressure remains stable, clear the code and test under load.

4. 4

   Post-repair calibration

   After replacing the DEF pump module, the new unit must be programmed/calibrated to the vehicle using the EST. Clear all permanent fault codes and run multiple driving cycles to verify the fix.