Fendt 01.1.9E – A039 - MFA (Multifunction Armrest): Communication error to the hand throttle potentiometer

The tractor's control system loses the signal from the hand throttle lever. As a safety and operational consequence, the Tractor Management System (TMS) is automatically switched off until the next cold start, and the hand throttle functions are deactivated. The tractor will typically enter a restricted operating mode where engine speed can only be controlled via the foot accelerator pedal position sensor (B029).

• 922 Vario COM III
• 924 Vario COM III
• 927 Vario COM III
• 930 Vario COM III
• 933 Vario COM III
• 936 Vario COM III
• 300 Vario Series
• 309
• 310
• 311
• 312
• 313
• 400 Vario Series
• 409
• 411
• 412
• 415
• 500 Vario Series
• 512
• 513
• 514
• 516
• 700 Vario Series
• 711
• 712
• 714
• 716
• 800 Vario Series
• 815
• 817
• 818
• 820
• 900 Vario Series
• 916
• 920
• 924
• 926
• 930
• 933
• 936

1. 1

   Visual & Mechanical Inspection: Check the mechanical linkage of the hand throttle lever to the position sensor inside the armrest. Ensure nothing is physically broken or binding.

2. 2

   Wiring & Connector Check: Access the inside of the A039 Multifunction Armrest. Inspect the wiring harness and connectors going to the hand throttle potentiometer (B035) for discontinuities, short circuits, backed-out pins, or corrosion.

3. 3

   Voltage Supply Test: Using a multimeter, check the voltage supply to the potentiometer. Depending on the exact model year, the reference voltage should be a steady 5V or 8.0V–8.5V.

4. 4

   Signal Test: Check the signal output of the potentiometer across its physical sweep (from idle to full power). The OEM specified current values are typically 16mA - 22mA at idle position and 2mA - 8mA at full power. If the signal is erratic, drops out, or reads out of range (I < 2mA or I > 22mA), the sensor is defective.

5. 5

   CAN Bus Check: Verify that there are no broader CAN communication failures between the MFA (A039) and the Basic Control Unit (A050).

1. 1

   Power Down

   Turn off the tractor ignition and disconnect the battery ground to prevent electrical shorts while working inside the armrest.

2. 2

   Disassemble the Armrest

   Carefully remove the covers of the A039 Multifunction Armrest to access the internal control boards and lever mechanisms.

3. 3

   Remove the Defective Sensor

   Locate the hand throttle potentiometer (B035) attached to the hand throttle lever assembly. Disconnect its electrical connector and unbolt the sensor/lever assembly from the console housing.

4. 4

   Install the New Part

   Mount the replacement potentiometer or complete hand throttle lever assembly. Reconnect the wiring harness, ensuring the connector clicks securely into place.

5. 5

   Reassemble

   Reinstall the armrest covers and restore battery power.

6. 6

   Calibration

   Turn the ignition ON. You must calibrate the new hand throttle sensor so the ECU learns the new idle and full-throttle end stops. Access the tractor's terminal calibration menu and run Calibration Code 4002 (Hand Throttle Calibration).

7. 7

   Clear Codes & Test

   Connect your diagnostic tool (e.g., FENDIAS or Jaltest), clear the 01.1.9E fault code, and test the tractor to ensure TMS can be engaged and the hand throttle operates the engine RPM smoothly.