John Deere 3516.07 – ECU: Aftertreatment DEF Concentration Sensor Obstructed

The DEF (Diesel Exhaust Fluid) tank fluid concentration sensor has detected debris obstructing the sensor, or the DEF concentration is reading extremely low/contaminated.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5090M
• 5100M
• 5100MH
• 5100ML
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• S-Series Combines (S650, S660, S670, S680, S690, S760, S770, S780, S790)
• T-Series Combines
• W-Series Combines
• X9 Series Combines
• 8R / 8RT / 8RX Series Tractors (8245R to 8400R, 8R 250 to 8R 410)
• 9R / 9RT / 9RX Series Tractors
• 7R Series Tractors
• 6M / 6R Series Tractors (6105M, 6120M, 6175M, 6215R)
• 5M / 5E / 5R Series Tractors
• 333G Skid Steers
• 544K Loaders
• 710L Backhoes
• Motor Graders

1. 1

   Test DEF Quality: Use a refractometer to test the DEF fluid in the tank. It must be exactly 32.5% urea. If the fluid is diluted or contaminated, this will trigger the code.

2. 2

   Inspect for Debris: Check the DEF tank for physical debris, crystallization, or foreign contaminants that could be physically blocking the sensor pickup.

3. 3

   Check Wiring/Connections: Inspect the wiring harness and connector at the DEF header for corrosion, heat damage, or loose pins.

4. 4

   Review Dealer Advisories: Check machine data to determine if the DEF header itself is failing and requires replacement.

1. 1

   Drain and Clean

   If the DEF is contaminated or debris is found, completely drain the DEF tank and flush/clean it to remove any obstructions.

2. 2

   Replace the DEF Header

   If the fluid was good or cleaning the tank does not clear the active code, the DEF Tank Header Assembly must be replaced. The concentration sensor is integrated into this header unit.

3. 3

   Refill

   Refill the tank with fresh, high-quality, OEM-spec Diesel Exhaust Fluid.

4. 4

   Reset and Test

   Reset the ECU to clear the fault code. Run the machine and conduct an emissions test/regen to ensure the aftertreatment system is operating efficiently and the code does not return.