Fendt 1.2.B4 – A020 / A021: CAN Message failure: from Pump Control to EDC Control Module

This fault code indicates that the CAN bus communication connection between the engine's injection pump control unit and the main engine control module has been interrupted or is faulty. When this communication is lost, the engine defaults to a restricted operating mode. The engine will drop to an idle (typically around 720 rpm), and the tractor will experience a loss of enhanced features, leaving only the foot throttle available.

• 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
• Favorit 900 Series (916, 920, 924, 926, 930 Vario)
• Favorit 700 Series
• Farmer 400 Series
• Fendt 300, 400, 700, 800, and 900 Vario (COM III) models

1. 1

   Consult the EDC Control circuit diagram to identify the specific CAN bus routing between the A020 and A021 modules

2. 2

   Inspect the CAN bus wiring harness and connectors between the EDC control module (A021) and the pump control unit (A020) for physical damage, breaks, corrosion, or loose pins

3. 3

   Verify the power supply and fuses for the CAN bus circuit board

4. 4

   Check for accompanying auto-diagnostic fault codes (such as 1.2.B5, 1.2.B6, or 1.2.B9) which indicate an internal EEPROM, RAM, or checksum failure inside the A020 Pump Control Unit itself

1. 1

   Disconnect Power

   Disconnect the tractor's batteries before servicing the EDC electrical components.

2. 2

   Access the Modules

   Locate the A021 EDC Control Module and the A020 Pump Control Unit (mounted on top of the Bosch VP44 injection pump).

3. 3

   Test Continuity

   Using a multimeter, test the continuity of the CAN High and CAN Low lines between the two modules.

4. 4

   Repair Wiring

   If resistance is high or the circuit is open, repair or replace the damaged section of the CAN bus wiring harness or the terminal connectors.

5. 5

   Address Module Failure

   If the wiring harness is fully intact and has good continuity, the fault likely resides in the CAN transceiver of either the EDC Control Module or the Pump Control Unit. Because the A020 module is subjected to extreme engine heat and vibration, the VP44 pump's integrated control unit is a highly common failure point.

6. 6

   Replace the Pump/Module

   Replace the faulty module. If the A020 unit is the culprit, this usually requires replacing or remanufacturing the entire Bosch VP44 injection pump assembly.

7. 7

   Clear and Test

   Reconnect the batteries, clear the fault codes using the FENDIAS diagnostic tool, and verify that CAN communication is restored and the engine responds to throttle inputs normally.