Fendt 6.1.50 – Enhanced Control Unit (E-box): Rear PTO stub shaft Hall-effect speed sensor plausibility error or signal fault

Fault code 6.1.50 (B020) indicates a plausibility error or signal fault with the Rear PTO stub shaft Hall-effect speed sensor. The system logs this code under two primary conditions: 1. Overspeed / Signal Fault: The speed at the PTO stub shaft is registered as > 1300 rpm, indicating a signal fault in the Hall-effect sensor (B020 or B021). 2. Underspeed / Solenoid Issue: The selected PTO speed is active, but the speed at the stub shaft is lower than the clutch speed. This points to a power supply fault to the Hall-effect sensor (B020), or the speed selection solenoid valves (Y026, Y027, Y028) are stuck in the 'OFF' position, wrongly wired, or mechanically seized. Consequence: Normal PTO operation is disabled, but activating speeds remains possible in 'emergency mode' by pressing and holding the 'Engage PTO' key in the cab for more than 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 400 Vario series
• Favorit 700 series
• Favorit 900 series
• 300 Vario series
• 400 Vario series
• 700 Vario series
• 800 Vario series
• 900 Vario series
• Vario series COM III generation

1. 1

   Emergency Mode Test: Press and hold the 'Engage PTO' button for 5 seconds. If the PTO engages, the mechanical clutch is functioning, confirming the issue is electrical (sensor, wiring, or solenoid).

2. 2

   Power Supply Check: Test the 12V power supply to the B020 Hall-effect sensor. Check the associated fuse (often A013) for the Enhanced Control circuit.

3. 3

   Wiring Inspection: Inspect the wiring harness and connectors for the B020 (stub shaft) and B021 (clutch) speed sensors for corrosion, chafing, or breaks.

4. 4

   Solenoid Valve Test: Test the speed selection solenoid valves (Y026 for Stage 1/540 rpm, Y027 for Stage 2/1000 rpm, Y028 for Stage 3). Ensure they are receiving voltage and are not mechanically seized or stuck in the 'OFF' position.

1. 1

   Access the Rear PTO Housing

   Locate the B020 Hall-effect speed sensor mounted on the rear PTO stub shaft assembly.

2. 2

   Test the Sensor

   Using a multimeter, verify the sensor's ground and 12V reference voltage. If voltage is correct but the sensor outputs an erratic signal (or reads >1300 rpm falsely), the sensor has failed internally.

3. 3

   Replace the Sensor

   Remove the retaining bolt, pull the old B020 sensor from the housing (ensure the O-ring is removed), lubricate the new O-ring, and install the replacement sensor.

4. 4

   Inspect Solenoids (If Sensor is Good)

   If the sensor tests fine, locate the PTO speed selection solenoid block (Y026, Y027, Y028). Remove the solenoids and inspect for debris or mechanical binding. Clean or replace any seized valves.

5. 5

   Clear Codes

   Connect the FENDIAS diagnostic tool (or use the tractor's terminal) to clear the 6.1.50 fault code.

6. 6

   Operational Test

   Engage the PTO normally (without holding the button for 5 seconds) to verify the repair.