Fendt 4.1.71 – A004 - ECU, control panel: Key fault / Key failure ('Cruise control 2' key)

The 'Cruise control 2' key is malfunctioning (often stuck, shorted, or failing to send the correct signal), preventing the cruise control from being activated. This can also represent a CAN bus failure from the A004 module to the Transmission Control Module.

• 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 and 900 series
• Fendt 400, 700, 800, and 900 Vario series (including COM III models)

1. 1

   Inspect the 'Cruise control 2' key on the A004 control console to see if it is physically stuck, jammed by debris, or damaged.

2. 2

   Check fuse board A013, specifically fuses F040 and F041, to ensure the CAN-Bus voltage supply fuses are not blown.

3. 3

   Inspect the wiring harness and CAN bus connections between the A004 control console and the Transmission Control Module for continuity, corrosion, or breaks.

4. 4

   Use FENDIAS or an AGCO 2x4 CANUSB diagnostic scanner to read the live state of the switch and attempt to clear the code to see if it actively returns.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent electrical shorts during the repair.

2. 2

   Clean the Switch

   If the 'Cruise control 2' button is physically stuck, carefully clean around the button housing using an appropriate electronic contact cleaner to free it from dirt or sticky residue.

3. 3

   Repair Wiring

   If diagnostic testing revealed a break or short in the CAN bus wiring between the A004 console and the transmission ECU, repair the damaged section of the harness.

4. 4

   Remove the Console

   If the button is internally broken or the console's circuit board has failed, the A004 control console must be removed. Disconnect the main harness connectors from the bottom/rear of the console.

5. 5

   Repair or Replace

   The A004 console is a complex electronic component. You must either replace it with a new OEM unit or send the defective console to a specialized agricultural electronics repair service (such as Ilgenfritz Mechatronics or RCC Electronique) for internal circuit board/switch repair.

6. 6

   Reinstall and Clear Codes

   Install the repaired or new A004 console. Reconnect the battery, turn on the ignition, and use the FENDIAS diagnostic tool to clear the stored 4.1.71 fault code. Test the cruise control function to verify the repair.