Massey Ferguson 003516.11 – ECU: DEF Quality Sensor Obstructed

The DEF quality sensor has detected a physical obstruction or contamination on its surface, such as crystallized DEF, debris, or other foreign material. This prevents the sensor from accurately measuring the concentration, temperature, and level of the Diesel Exhaust Fluid (DEF). This condition disrupts the proper functioning of the Selective Catalytic Reduction (SCR) system and may trigger an engine power reduction or limp mode to ensure compliance with emissions regulations.

• 5710SL
• 5711SL
• 5712SL
• 5713SL
• 7714
• 7715
• 7715S
• 7716
• 7716S
• 7718
• 7718S
• 7719
• 7720
• 4700 Series
• 5600 Series
• 7600 Series

1. 1

   Visually inspect the DEF tank for signs of contamination; the DEF should be a clear, colorless liquid.

2. 2

   Test the DEF quality using a refractometer to ensure the urea concentration is at the required 32.5%.

3. 3

   Inspect the wiring harness and electrical connectors leading to the DEF header assembly for corrosion, damage, or loose connections.

4. 4

   Check for frozen DEF in the tank during cold weather, as this can trigger sensor faults.

5. 5

   Review the system for other active or inactive SCR-related fault codes (e.g., DEF temperature or level) to provide additional diagnostic context.

1. 1

   Prepare machine and ensure safety

   Turn the engine off and disconnect the battery to prevent electrical hazards. Wear appropriate personal protective equipment (gloves and eye protection) as DEF can cause skin irritation.

2. 2

   Remove DEF header assembly

   Locate the DEF header mounted on top of the DEF tank. Disconnect the electrical harness and any fluid lines attached to the header. Unbolt the assembly from the tank and carefully remove it, preparing for minor DEF spillage.

3. 3

   Clean the sensor

   Inspect the sensor probes for crystallized DEF or debris. Gently clean the surfaces using a soft, lint-free cloth and a DEF-compatible cleaning solution, de-ionized water, or isopropyl alcohol (90% or higher). Do not use abrasive materials. For stubborn crystallized deposits, allow the cleaning solution to soften them before wiping. Ensure the sensor is completely dry before reinstallation.

4. 4

   Inspect and clean DEF tank

   With the sensor assembly removed, inspect the inside of the DEF tank for debris or contamination. If contamination is found, drain and clean the tank according to the manufacturer's recommendations.

5. 5

   Reinstall sensor assembly

   Carefully reinstall the cleaned sensor assembly using a new gasket. Reconnect all electrical and fluid lines, ensuring secure connections.

6. 6

   Clear codes and recalibrate

   Reconnect the battery and use a diagnostic tool to clear the 003516.11 fault code. Perform several key cycles (turning ignition on and off) or drive the vehicle to allow the ECU to recognize the new sensor readings and recalibrate. If the fault code reappears, replace the DEF quality sensor assembly.