Case IH 3593 – Engine Control Unit (ECU): Poor Reagent quality

The Selective Catalytic Reduction (SCR) system has detected that the Diesel Exhaust Fluid (DEF / AdBlue) in the tank does not meet the required urea concentration threshold (typically 32.5%), or the sensor reading the fluid is malfunctioning.

• Puma
• Puma 170
• Puma 210
• Magnum
• Steiger
• Maxxum
• Farmall
• SV series
• SV340B
• TR series
• TR340
• Axial-Flow series
• Axial-Flow 6130

1. 1

   Test the DEF fluid currently in the tank using a DEF refractometer (must read exactly 32.5% urea concentration)

2. 2

   Inspect the DEF tank for signs of water dilution, diesel fuel contamination, or dirt/debris

3. 3

   Inspect the DEF Quality Sensor / Head Unit wiring harness and connector at the tank for corrosion, moisture, or physical damage

4. 4

   Check the DEF injector (doser) nozzle at the exhaust for severe crystallization or clogging

1. 1

   Drain and Flush

   If the DEF tests poorly or is contaminated, completely drain the DEF tank. Flush the tank with distilled water or fresh DEF (never use tap water or chemicals).

2. 2

   Replace the DEF Filter

   Always replace the main DEF supply filter when dealing with contaminated fluid to protect the dosing pump.

3. 3

   Refill

   Fill the tank with fresh, API-certified Diesel Exhaust Fluid.

4. 4

   Sensor/Injector Replacement

   If the fluid is perfectly fine but the code persists, the DEF Quality Sensor (integrated into the DEF Head Unit) has likely failed internally and must be replaced. In some cases, a faulty DEF injector failing to dose properly can also trigger this fault.

5. 5

   Clear Codes

   Use the Case IH Electronic Service Tool (EST) to clear the fault codes, or run the machine through a stationary regeneration cycle to allow the ECU to sample the new fluid and reset the system.