Case IH 17682 (F-3364-05) - ECU – Engine Control Unit (ECU): DEF/AdBlue Quality Sensor Signal Shorted to Ground

Internal failure of the DEF/AdBlue quality sensor, specifically that the quality signal is shorted to ground. The control module is receiving a voltage signal from the sensor that is lower than the expected operating range (near zero volts). This condition is typically caused by a wiring harness short to ground, connector corrosion, or an internal short-circuit within the sensor's electronic circuit board.

• VESTRUM CVX
• Farmall (40-45-50, 90C-120C)
• Maxxum (110-150)
• Puma (130-240)
• Magnum
• Steiger
• Quadtrac
• Austoft 9900
• Axial-Flow combines

1. 1

   Inspect the DEF quality sensor wiring harness and electrical connector for physical damage, chafing, or exposed wires touching the chassis (short to ground).

2. 2

   Disconnect the sensor and check the pins for corrosion. A known issue with these systems is ammonia gas from the DEF fluid leaking into the sensor housing, which corrodes the internal circuit boards and connector pins.

3. 3

   Measure the voltage and resistance (ohms) at the sensor connector to verify if the short is in the machine's wiring harness or internal to the sensor itself.

4. 4

   Unplug the DEF quality sensor. If the active fault code changes from a 'short to ground' to an 'open circuit' (or if a downed CAN bus comes back online), the fault is isolated internally to the sensor, meaning the sensor must be replaced.

1. 1

   Power Down

   Turn off the machine and disconnect the battery to prevent electrical spikes during the repair.

2. 2

   Locate the Sensor

   Locate the DEF quality sensor, which is integrated into the DEF delivery system. It is typically mounted on the DEF header assembly at the top or bottom of the DEF/AdBlue tank.

3. 3

   Disconnect

   Unplug the electrical wiring harness connector from the sensor.

4. 4

   Removal

   Remove the mounting hardware and carefully extract the faulty DEF quality sensor (or the entire DEF header unit, depending on the specific tank design) from the tank.

5. 5

   Clean

   Clean the mounting surface on the tank to ensure a proper seal and prevent contamination of the DEF fluid.

6. 6

   Installation

   Install the new DEF quality sensor and secure it with the mounting hardware.

7. 7

   Reconnect

   Reconnect the electrical wiring harness and then reconnect the machine's battery.

8. 8

   Clear Codes

   Use a diagnostic service tool or the in-cab AFS Pro display to clear the stored fault codes.

9. 9

   Test

   Run the engine and verify that the SCR/DEF system operates normally without triggering the fault code or engine derate.