Case IH F-5392-14 - ECU – Engine Control Unit (ECU) or Dosing Control Unit (DCU): DEF/AdBlue system unable to build sufficient pressure for dosing

The Selective Catalytic Reduction (SCR) system cannot generate or maintain the required fluid pressure (4900 to 6200 millibar) to inject Diesel Exhaust Fluid (DEF) into the exhaust stream, leading to emissions spikes and a progressive power derate.

• MAGNUM AFS Connect
• Puma (150, 175, 185)
• Maxxum (115-150)
• Magnum (180-380)
• Steiger (e.g., 450)
• Farmall (40-50, 110A-140A)
• 240 Series Axial-Flow Combines (7240, 8240, 9230, 9240)
• Patriot Series Sprayers (2250, 3240, 3340)

1. 1

   Verify Fluid Quality: Inspect the DEF/AdBlue tank for poor fluid quality, contamination, or crystallization.

2. 2

   Check for Suction Leaks (WEMA Unit): Inspect the DEF tank pickup tubes (WEMA units). Pressurize the tube slightly to check for hairline leaks, as cracked tubes cause the pump to draw air.

3. 3

   Run a Pressure Test: Use the Case IH Electronic Service Tool (EST) to perform the Urea Dosing System Test (UDST). Confirm that the system pressure reaches 4900 to 6200 millibar (71.1 to 89.9 psi) and that evacuation pressure is between -50 and -300 millibar (-0.72 and -4.35 psi).

4. 4

   Inspect the Dosing Injector: Remove and inspect the DEF injector nozzle at the exhaust. Crystallized deposits can restrict flow, causing pressure plausibility faults.

5. 5

   Inspect Wiring: Check the wiring harness near the exhaust. The SCR system lives in a high-heat environment, which can destroy insulation and cause intermittent signal dropouts to the pump.

1. 1

   Flush the System

   If the DEF fluid is contaminated or highly crystallized, drain the tank and flush the system completely before installing any new parts.

2. 2

   Replace the DEF Filter

   If the pump is struggling to build pressure but no leaks are found, replace the DEF filter.

3. 3

   Address Suction Leaks

   If the pickup tube is cracked, replace the WEMA sending unit assembly in the tank. (Note: Updated replacement units feature doubled-up O-rings to prevent future suction issues).

4. 4

   Clean/Replace the Injector

   If the dosing valve is mechanically blocked by crystallized DEF, clean the nozzle or replace the injector assembly.

5. 5

   Replace the DEF Pump

   If the system fails the EST pressure test, wiring is intact, and there are no suction leaks, the DEF pump (supply module) has failed internally and must be replaced.

6. 6

   Reprogramming

   A new DEF pump/dosing module must be programmed to the vehicle's ECU after replacement using the dealer service tool.

7. 7

   Clear Codes

   Clear the fault codes and run the machine under load to ensure the derate is lifted and the system 'heals'.