CLAAS Id78B2h / 78B2h (842) – TR2 (A57-2) Transmission Module: Transmission module TR2 (A57-2) has detected a communication loss with the external function module EXT (A62) during a CSM sequence.

The immediate system response to this fault is that the Drivestick is disconnected.

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

1. 1

   Check the TR2 transmission module (A57-2) and the external function module EXT (A62) for physical damage or signs of water ingress.

2. 2

   Verify all relevant fuses, 12V power supply voltages, and ground connections to both the TR2 and EXT modules.

3. 3

   Inspect the connectors and test the continuity of the wiring harnesses linking the TR2 and EXT modules (specifically the CLAAS vehicle CAN bus network).

4. 4

   Check for CAN bus faults, including short-circuits to 12V, short-circuits to ground, or open circuits on the CAN bus lines.

1. 1

   Verify Power and Ground

   Locate the TR2 module (often located behind the driver's seat, "Auto 5" type module with a 42-terminal connector) and the EXT module. Use a multimeter to ensure both modules are receiving stable battery voltage and have clean ground connections.

2. 2

   Inspect the CAN Bus

   Back-probe the CAN High and CAN Low wires between the TR2 and EXT modules. Verify that the CAN bus terminating resistors are intact (typically reading ~60 ohms across the network when powered down).

3. 3

   Repair Wiring

   If any open circuits, shorts to ground, or shorts to power are found in the harness between A57-2 and A62, repair or replace the damaged wiring section.

4. 4

   Test the Modules

   If the wiring, power, and grounds are perfectly intact, one of the modules has likely suffered an internal failure. Test the TR2 ("Auto 5") module using CLAAS special tool n° 60 05 033 249 (or the CLAAS Diagnostic System - CDS).

5. 5

   Replace and Calibrate

   Change the faulty module (TR2 or EXT) if it fails the diagnostic tool test. Ensure you check the compatibility of program versions and perform any required settings/calibrations via the CDS after installation.