Case IH F-3521-09 - ECU – Engine Control Unit (ECU) or Aftertreatment Control Module (ACM) / Dosing Control Unit (DCU): CAN timeout error from DEF/AdBlue quality sensor

The control module has lost communication with the DEF quality sensor over the CAN bus network, or the sensor is failing to broadcast its fluid quality data within the expected timeframe.

• MAGNUM AFS Connect
• Magnum series (180–380)
• Steiger
• Quadtrac (350–600)
• Maxxum
• Puma
• Farmall
• Axial-Flow series (240 series, 5130, 6130, 7130, 7230, 8230, 9230)
• Patriot / Titan series (3030, 3530, 4030, 4530)

1. 1

   Verify ECM Calibration: Ensure the engine ECM is updated to the latest software calibration, as outdated software is a known cause of false sensor timeouts.

2. 2

   Check DEF Level: Verify the DEF tank is not low, as low fluid can cause sloshing and air bubbles, leading to miscalculations and dropped signals.

3. 3

   Test DEF Quality: Use a refractometer to verify the DEF concentration is exactly 32.5%. Contaminated or degraded fluid can trigger this code.

4. 4

   Inspect for Ammonia Corrosion: Check if ammonia gas from the DEF tank has vented into the sensor housing and corroded the internal circuit board.

5. 5

   Check Wiring and CAN Bus: Inspect the wiring harness and electrical connector at the DEF header for moisture, corrosion, or damaged pins.

1. 1

   Turn off the machine and disconnect the battery

   Turn off the machine and disconnect the battery to prevent electrical shorts.

2. 2

   Locate the DEF tank and header unit

   Locate the DEF tank and the DEF header unit (which houses the quality sensor, level sensor, and pickup tubes).

3. 3

   Disconnect the electrical harness

   Disconnect the electrical harness from the DEF header.

4. 4

   Disconnect the DEF lines

   Disconnect the DEF supply and return lines from the top of the header.

5. 5

   Remove mounting hardware

   Remove the mounting bolts or retaining ring securing the DEF header to the tank.

6. 6

   Extract the old DEF header

   Carefully extract the old DEF header assembly from the tank.

7. 7

   Insert the new DEF header assembly

   Insert the new DEF header/quality sensor assembly, ensuring the gasket/O-ring is properly seated to prevent leaks.

8. 8

   Secure the header and reconnect

   Secure the header and reconnect the DEF lines and electrical harness.

9. 9

   Reconnect battery and clear codes

   Reconnect the battery, turn the key on, and use a diagnostic scan tool (such as Jaltest or the Case IH AFS Pro display) to clear the fault codes.

10. 10

    Run the engine

    Run the engine to verify the SCR system initializes without triggering the F-3521-09 code.