CLAAS Id78BDh / 78BDh (853) – TR3 (A57-3) Transmission Module: Communication loss with the External function module EXT (A62)

The Transmission module TR3 (A57-3) has detected a communication loss with the External function module EXT (A62) over the vehicle's CAN bus network during a CSM (CLAAS Sequence Management) sequence. As a direct system response, the tractor will automatically disconnect the front power take-off (PTO), rendering it inoperative.

• CLAAS Axion 800 Series (810, 840, 850)
• CLAAS Axion 900 Series (920, 950)
• CLAAS Arion 400 Series (410, 430)
• CLAAS Arion 500 / 600 Series (510, 640)

1. 1

   Verify the operational status of both the TR3 transmission module (A57-3) and the EXT external function module (A62)

2. 2

   Test the CLAAS vehicle CAN bus network for communication errors, as the EXT module may have stopped transmitting messages due to a high frame error rate

3. 3

   Check the connectors and continuity of the harnesses linking the TR3 and EXT modules, looking for open circuits or short-circuits

4. 4

   Verify the sources of energy for both modules, including all relevant fuses, power supply lines, and ground connections

5. 5

   Check the compatibility of the program versions, settings, and calibration between the modules using the CLAAS Diagnostic System (CDS)

1. 1

   Hard Reset

   Turn off the tractor's main battery switch, wait for at least 30 seconds, and restart the engine. This allows the modules to power down completely and attempt to re-establish CAN communication.

2. 2

   CSM Reset

   The tractor will normally attempt to initialize and relaunch the sequence after 20 seconds. If nothing happens and the front PTO remains inoperative, manually reset the CSM (CLAAS Sequence Management) via the Cebis terminal.

3. 3

   Harness Repair

   If the fault persists, physically inspect the CAN bus wiring harness between the TR3 (located behind the driver's seat) and the EXT module. Clean any corroded connector pins and repair any damaged wires causing a short or open circuit.

4. 4

   Software Update

   Connect the CLAAS Diagnostic System (CDS) to check for software updates or re-flash the TR3 and EXT modules to clear logic errors.

5. 5

   Module Replacement

   If wiring, power, and grounds are all verified to be good but communication cannot be restored, replace the faulty module (either the TR3 or EXT module) and calibrate it to the tractor.