CLAAS Id78D3h / 78D4h – EXT (A62) - External Function Module: CAN Communication Failure (Ignition off / Contacts S1 or S2)

CAN communication failure where specific messages are either not received or contain invalid values. Id78D3h indicates the CAN 'Ignition off' message is not received by the external function module or has an invalid value. Id78D4h indicates the CAN 'Contacts S1 or S2' message is not received by the external function module or has an invalid value.

• Axion 800 Series (810, 850)
• Axion 900 Series (920, 950)
• Arion 500/600 Series (510, 640)

1. 1

   For Id78D3h: Check the Lifting Module REH (A58), the Bus CAN network communication module BDG (A103), and the External Function Module EXT (A62)

2. 2

   For Id78D4h: Check the Armrest Multifunction Module MFA (A100) and the External Function Module EXT (A62)

3. 3

   Check for any short-circuits or open circuits in the CLAAS vehicle CAN bus network wiring

4. 4

   Check the sources of energy (fuses, power supply, and ground) for the affected modules

5. 5

   Check the connectors and continuity of harnesses linking each component

6. 6

   Verify the compatibility of program versions, settings, and calibration across the modules

1. 1

   Verify the Code

   Use the Cebis terminal or a diagnostic tool to confirm which specific code is active and whether it is currently passive or active.

2. 2

   Inspect Wiring & Connectors

   Locate the EXT (A62) module and the corresponding sender module (REH A58, BDG A103, or MFA A100 depending on the code). Disconnect the harnesses and inspect the pins for corrosion, moisture, or physical damage.

3. 3

   Test Power and Ground

   Using a multimeter, verify that the EXT (A62) module and the corresponding sender modules are receiving proper 12V power and have a solid ground connection.

4. 4

   Test CAN Bus Continuity

   Measure the resistance of the CAN bus lines between the modules to ensure there are no breaks or shorts to ground/power in the harness.

5. 5

   Module Replacement

   If the wiring, power, and ground are all intact, the fault lies within the internal circuitry of one of the modules failing to broadcast or receive the CAN message. Replace the faulty component (EXT, BDG, REH, or MFA module).

6. 6

   Calibration

   If a module is replaced, ensure it is flashed with the correct software version and calibrated to the tractor's specific configuration. Clear the fault codes and test the ignition and armrest controls to verify the repair.