Fendt B.1.21 – A002 - ECU, enhanced control: A002 - ECU, enhanced control — CAN Bus communication fault in TI automatic operation

This fault code indicates a CAN bus communication error involving the Variotronic TI (Tractor Management System / "Teach-in") automatic operation. The underlying condition is that the enhanced control ECU has lost data transfer communication with the Teach-in system. As a direct consequence, the Variotronic TI automatic operation (Teach-in) will not function.

• 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
• Fendt Farmer 400
• Fendt Favorit 700
• Fendt Favorit 900
• FENDT 300 Vario (COM III)
• FENDT 400 Vario (COM III)
• FENDT 700 Vario
• FENDT 700 Vario (COM III)
• FENDT 800 Vario
• FENDT 800 Vario (COM III)
• FENDT 900 Vario
• FENDT 900 Vario (COM III)

1. 1

   Check voltage supply to the CAN-Bus on the A013 fuse board, specifically fuses F040 and F041

2. 2

   Look for accompanying fault codes (e.g., B.1.22, B.1.23, B.1.24) that would indicate a broader CAN bus failure rather than an isolated module issue

3. 3

   Inspect the wiring harness and main connectors (such as X031) between the A002 E-Box and the Variotronic terminal for pushed pins, moisture, or corrosion

4. 4

   Verify software status using FENDIAS diagnostic software to ensure the E-Box EEPROM is not corrupted

1. 1

   Power Down

   Turn off the tractor ignition and disconnect the negative battery terminal to prevent electrical spikes.

2. 2

   Fuse Inspection

   Locate the A013 printed circuit board (fuse board). Inspect and test fuses F040 and F041. Replace them if they are blown.

3. 3

   Harness Inspection

   Locate the A002 E-Box. Disconnect the main wiring harness connectors (e.g., X031) and inspect the pins. Clean any corrosion using electrical contact cleaner.

4. 4

   Continuity Testing

   Using a multimeter, perform a continuity test on the CAN High and CAN Low wires between the A002 E-Box and the Variotronic terminal (A008). Repair any breaks or chafed wires in the harness.

5. 5

   Reconnection and Clearing

   Reconnect the wiring harnesses and the battery. Turn the ignition on. Use the FENDIAS diagnostic tool or the tractor's onboard diagnostic menu to clear the stored B.1.21 fault code.

6. 6

   Functional Test

   Start the tractor and attempt to engage the Variotronic TI (Teach-in) function.

7. 7

   Module Reprogramming/Replacement

   If the wiring is intact and the fault returns immediately, the A002 E-Box may have suffered an internal failure or EEPROM corruption. It will need to be re-flashed (End-of-Line / EOL programming) by a dealer or replaced entirely.