Fendt 1.2.91 – EDC (Electronic Diesel Control) Control Module (A021) and Pump Control Unit (A020): EDC speed sensor — Signal fault

Signal failure or implausible signal (statically or dynamically) from the B025 engine speed sensor. The system detects that the engine speed data is missing or incorrect, causing the tractor to enter a restricted operating mode (reducing full power flow by 25-40% and limiting the maximum engine speed to 1800 RPM).

• 409 Vario
• 410 Vario
• 411 Vario
• 412 Vario
• 711 Vario
• 712 Vario
• 714 Vario
• 715 Vario
• 716 Vario
• 717 Vario
• 718 Vario
• 916 Vario
• 920 Vario
• 924 Vario
• 926 Vario
• 930 Vario
• Farmer 400 series
• Favorit 700 series
• Favorit 900 series
• Vario 300 series
• Vario 400 series
• Vario 500 series
• Vario 700 series
• Vario 800 series
• Vario 900 series
• 309-939 Vario models

1. 1

   Visually inspect the B025 sensor located on the left side of the tractor on the flywheel housing.

2. 2

   Check the sensor tip for interference caused by metallic chips stuck to the magnetic sensor.

3. 3

   Verify the installation clearance distance between the sensor and the flywheel is correct.

4. 4

   Inspect the sensor's wiring harness and connector X172 for wire disruption, short circuits, or swapped poles (Pin 1 is Earth, Pin 2 is Signal).

5. 5

   Perform a voltage test to check the voltage supply and earth at the EDC Control Module (A021) using an adapter box to ensure the module is properly powering the sensor circuit.

1. 1

   Disconnect battery

   Turn off the tractor and disconnect the battery to ensure safety while working on the EDC circuit.

2. 2

   Locate sensor

   Open the left side of the bonnet and locate the B025 engine speed sensor on the flywheel housing.

3. 3

   Inspect connector

   Disconnect the X172 connector and inspect the pins for corrosion or damage.

4. 4

   Clean sensor

   Unbolt and remove the B025 sensor. Wipe it clean of any metallic debris or oil sludge.

5. 5

   Reinstall and test

   If the sensor was heavily fouled, reinstall it, reconnect the harness, and test the tractor.

6. 6

   Replace sensor

   If the wiring is intact and cleaning the sensor does not resolve the fault, the sensor has failed internally. Install a new OEM speed sensor.

7. 7

   Clear fault codes

   Connect the FENDIAS diagnostic tool to the tractor, record the failure and ambient parameters, and delete the failure memory.

8. 8

   Verify repair

   Start the engine and verify with FENDIAS that the fault code 1.2.91 does not return and that engine RPM reads correctly.