Case IH 17674 (F-3516-01) - ECU – Engine Control Unit (ECU) or Dosing Control Unit (DCU): DEF/AdBlue quality sensor detects concentration is too low (time based evaluation)

This fault code indicates that the Diesel Exhaust Fluid (DEF) quality sensor has detected that the urea concentration in the DEF tank has fallen outside the acceptable range (which should be 32.5% urea). This typically happens when the DEF has been diluted with water, has degraded due to age or extreme heat exposure, or if the DEF quality sensor itself has failed or drifted out of calibration.

• VESTRUM CVX
• Austoft 9900 sugarcane harvesters
• Farmall series tractors (40, 45, 50, 115U, 120A)
• Magnum series tractors
• Steiger / Quadtrac series tractors
• Axial-Flow combines (230 series)

1. 1

   Test the DEF fluid with a DEF refractometer to verify it reads exactly 32.5% urea concentration.

2. 2

   Inspect the DEF tank for signs of contamination, such as water, diesel fuel, or off-spec fluid.

3. 3

   Inspect the DEF quality sensor's electrical connector and wiring harness for corrosion, which can be caused by ammonia gas venting from the DEF fluid.

4. 4

   Check for sensor drift or internal electrical faults if the fluid tests perfectly at 32.5% but the code remains active.

1. 1

   Drain and Flush

   If the DEF fluid tests poorly, drain the DEF tank completely.

2. 2

   Refill

   Refill the tank with fresh, ISO 22241-compliant Diesel Exhaust Fluid.

3. 3

   Clear and Retest

   Clear the fault codes using a diagnostic tool and run the engine to see if the code returns.

4. 4

   Replace the Sensor/Header

   If the fluid is confirmed good but the code persists, the DEF quality sensor has failed. Depending on the specific machine model, you will need to replace either the standalone DEF quality sensor or the entire DEF header unit (sending unit) that drops into the tank.

5. 5

   Software Update Note

   Check with a Case IH dealer to see if your machine is eligible for a software update. Recent EPA regulation changes have allowed manufacturers to eliminate the requirement for the in-tank DEF quality sensor on some platforms, relying instead on the downstream NOx sensors to verify SCR system functionality.