Fendt 4.1.81 – Transmission Control Module: Engine speed Hall sensor 1/2 — Plausibility error (=speeds do not match)

This code indicates that the control unit is receiving conflicting or illogical signals between Engine Speed Hall Sensor 1 (B010) and Engine Speed Hall Sensor 2 (B011). Because the two speed indications do not correspond, the system flags a "plausibility failure". When this fault is active, the tractor will typically default to "Auxiliary Operation Mode" (emergency mode), though continuation of driving in this restricted state is usually possible.

• 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
• Fendt Farmer 400 Vario series
• 409
• 410
• 411
• 412
• Fendt Favorit 700 Vario series
• 711
• 712
• 714
• 716
• Fendt Favorit 900 Vario series
• 916
• 920
• 924
• 926
• 930
• Fendt 300 Vario (COM III)
• Fendt 400 Vario (COM III)
• Fendt 700 Vario (COM III)
• Fendt 800 Vario (COM III)
• Fendt 900 Vario (COM III)

1. 1

   Live Data Comparison: Use the FENDIAS diagnostic software or the tractor's terminal to monitor the live RPM data from both Sensor 1 (B010) and Sensor 2 (B011) simultaneously. Identify which sensor is dropping out, spiking, or reading a flat zero.

2. 2

   Wiring and Connector Inspection: Inspect the wiring harnesses leading to sensors B010 and B011. Look for chafing, breaks, or corrosion in the connectors, which are common causes of signal plausibility errors.

3. 3

   Sensor Debris/Damage: Remove the sensors and inspect the magnetic tips. Hall-effect sensors can attract metallic debris from the engine/transmission, which distorts the signal.

4. 4

   Tone Ring Inspection: Inspect the tone ring (or gear teeth) that the sensors read for physical damage or excessive runout.

1. 1

   Safety First

   Park the tractor on a level surface, engage the parking brake, turn off the engine, and disconnect the battery to prevent accidental short circuits during electrical work.

2. 2

   Locate the Sensors

   Locate the B010 and B011 Hall-effect speed sensors (typically mounted on the engine block near the crankshaft/flywheel or the transmission input housing, depending on the specific engine model).

3. 3

   Removal

   Disconnect the electrical connector from the faulty sensor. Remove the retaining bolt(s) securing the sensor to the housing and carefully pull the sensor straight out.

4. 4

   Cleaning

   Clean the mounting bore and the surrounding surface to ensure the new sensor seats perfectly flat. An improper seating depth will cause an incorrect air gap and trigger the same plausibility fault.

5. 5

   Installation

   Insert the new OEM Hall speed sensor. Install and tighten the retaining bolt to the manufacturer's specified torque.

6. 6

   Reconnection

   Reconnect the electrical harness, ensuring the weather-pack seal clicks firmly into place.

7. 7

   Clear Codes

   Reconnect the battery. Turn the ignition on and use the tractor's terminal or FENDIAS tool to clear the stored 4.1.81 fault code.

8. 8

   Test Drive

   Start the engine and verify that the tractor successfully exits Auxiliary/Emergency Operation Mode and that cruise control and standard transmission functions are restored.