Fendt 6.1.05 – Rear PTO Control Module: Hall-effect speed sensor at rear PTO clutch — Signal fault

The system detects a signal fault from the B021 Hall-effect speed sensor. This often means the actual speed of the PTO stub shaft (corrected by the transmission rate) differs from the specified setpoint speed of the PTO clutch by more than 12%, or the sensor signal is missing/erratic. The PTO will disengage or fail to engage normally. However, the PTO can still be engaged in emergency mode by pressing and holding the emergency PTO key (or "Engage PTO" cab button) for at least 5 seconds.

• 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
• 411 Vario COM III
• 412 Vario COM III
• 413 Vario COM III
• 414 Vario COM III
• 415 Vario COM III
• 712 Vario COM III
• 714 Vario COM III
• 716 Vario COM III
• 718 Vario COM III
• 818 Vario COM III
• 820 Vario COM III
• Farmer Series 300
• Farmer Series 400 (409, 410, 411, 412)
• Favorit Series 500
• Favorit Series 700
• Favorit Series 900
• Vario Series 200
• Vario Series 300
• Vario Series 400
• Vario Series 500
• Vario Series 700
• Vario Series 800
• Vario Series 900 (including COM III and S4 generations)
• Vario Series 1000

1. 1

   Check Power Supply: Verify the 12V supply to the sensor. Check the A013 PCB microfuses, specifically Fuse 33 (or Fuse 34 depending on the exact model year).

2. 2

   Inspect Wiring and Connectors: Inspect the wiring harness between the Rear PTO control module and the B021 sensor. Check separation point/connector X170 for corrosion, moisture, or damaged pins.

3. 3

   Check Solenoid Valves: Check the PTO solenoid valves (Y026, Y027, Y028) to ensure they are not incorrectly wired or mechanically seized, which can cause the clutch to slip.

4. 4

   Mechanical Inspection: Ensure there is no mechanical fault in the speed selector mechanism that would cause the clutch to slip or fail to reach the setpoint speed.

1. 1

   Locate the Sensor

   Locate the B021 Hall-effect speed sensor at the rear of the tractor, on the rear PTO clutch assembly (often near the PTO stub shaft where the B020 sensor is also located). You may need to detach the rear cover panel or the right rear wheel for better access depending on the model.

2. 2

   Disconnect the Battery

   Always disconnect the battery before servicing electrical sensors to prevent short circuits.

3. 3

   Remove the Sensor

   Disconnect the X170 electrical connector from the B021 sensor. Unbolt and carefully remove the inductive Hall-effect sensor from its mounting port on the PTO clutch housing.

4. 4

   Install the New Sensor

   Lubricate the O-ring on the new sensor (if applicable) and insert it into the housing. Secure it with the mounting bolt.

5. 5

   Reconnect and Reassemble

   Reconnect the X170 wiring harness. Reinstall any cover panels or wheels removed during access.

6. 6

   Clear Codes

   Reconnect the battery, turn the ignition on, and use the tractor's terminal or FENDIAS diagnostic tool to clear the stored 6.1.05 / B021 fault code. Test the PTO engagement to ensure normal operation without needing the 5-second emergency override.