Fendt 06.1.96 – A039 - MFA (Multifunction Armrest): A039 - MFA, multifunction armrest. Button 540, REAR PTO. Counter error.

The control unit has detected an invalid signal count, state mismatch, or internal logic error specifically originating from the button used to select the 540 RPM speed for the Rear Power Take-Off (PTO).

• 922 Vario COM III
• 924 Vario COM III
• 927 Vario COM III
• 930 Vario COM III
• 933 Vario COM III
• 936 Vario COM III
• Fendt 300 Vario (COM III)
• Fendt 400 Vario (COM III)
• Fendt 700 Vario (COM III / SCR)
• Fendt 800 Vario (COM III / SCR)
• Fendt 900 Vario (COM III / SCR)

1. 1

   Inspect the Rear PTO 540 button on the multifunction armrest for mechanical jamming, sticking, or damage.

2. 2

   Check for broader MFA bus faults (such as 00.0.03 A039 - MFA Multifunction armrest bus fault) which would indicate a total communication failure between the armrest and the basic control unit (A050).

3. 3

   Connect the FENDIAS diagnostic tool and monitor the live state of the PTO 540 button to see if it is registering phantom presses or is stuck in an active state.

1. 1

   Clear and Retest

   Connect the FENDIAS diagnostic system, clear the active fault codes, and cycle the tractor's ignition. Test the PTO 540 button to see if the counter error returns immediately.

2. 2

   EOL Programming

   Use FENDIAS to perform an EOL parameter reset/reprogramming on the A039 Multifunction Armrest to resync the module's counters.

3. 3

   Component Replacement

   If EOL programming fails to clear the counter error, or if the button is physically broken/shorted internally, the keypad module on the A039 multifunction armrest must be replaced.

4. 4

   Recalibration

   If any hardware on the MFA is replaced, you must perform EOL programming again to marry the new hardware to the tractor's basic control unit (A050).