Case IH 3594 (F-519874-31) - ECU – Engine Control Unit (ECU / ECM) or Vehicle Control Module (VCM): Torque limitation caused by SCR catalyst protection

This is an emissions inducement code. It means the system has detected a critical issue with the Selective Catalytic Reduction (SCR) system (such as poor Diesel Exhaust Fluid (DEF) quality, low DEF level, or a component failure) and has actively placed the engine into a derate mode (limiting torque and power) to protect the SCR catalyst from damage and to comply with emissions regulations.

• VESTRUM CVX
• Steiger
• Magnum
• Puma
• Maxxum
• Optum
• Farmall
• 240 Series Axial-Flow Combines
• Case N-Series TLBs and loaders

1. 1

   Check the ECU for other active primary SCR-related fault codes (e.g., NOx sensor plausibility, DEF dosing valve overheat, DEF quality/level warnings, or catalyst temperature sensor faults).

2. 2

   Verify the DEF/AdBlue tank is full and the fluid is not contaminated, degraded, or frozen.

3. 3

   Inspect the DEF dosing valve (injector) and exhaust injection port for severe DEF crystallization, blockages, or physical damage.

4. 4

   Monitor live data for the upstream and downstream NOx sensors and SCR temperature sensors to ensure they are reading within plausible ranges.

1. 1

   Address primary fault

   Repair or replace the component causing the primary SCR fault (e.g., replace a failed NOx sensor, clean or replace a clogged DEF dosing valve, or drain and refill the DEF tank with fresh fluid if contamination is found).

2. 2

   Clean dosing port

   If the dosing valve was clogged, manually clean any crystallized DEF from the mounting boss on the exhaust pipe.

3. 3

   Perform SCR system test

   Using the Case IH Electronic Service Tool (EST), run a DEF doser pump override test to ensure the new or cleaned valve is spraying correctly and building proper pressure.

4. 4

   Force regeneration cycle

   Initiate an SCR system warm-up cycle or forced regeneration via the EST. The ECU will not lift the torque limitation until it verifies the SCR system is fully functional.

5. 5

   Clear fault codes

   Once the system successfully completes the cycle and emissions are verified to be within the acceptable threshold, clear the inactive 3594 fault code to restore full engine torque.