CLAAS Id78B4h / 78B4h (844) – Transmission module TR2 (A57-2): Communication loss with external function module EXT (A62) during CSM sequence

The Transmission module TR2 (A57-2) has detected a communication loss with the external function module EXT (A62) during a CSM (CLAAS Sequence Management) sequence. As a system response, the automatic gear shifting is disconnected, and the CSM sequence is stopped.

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

1. 1

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

2. 2

   Check the connectors and the continuity of the harnesses linking the TR2 and EXT components.

3. 3

   Check for any short-circuits or open circuits on the CLAAS vehicle CAN bus network.

4. 4

   Check the sources of energy for both modules, including fuses, power supply voltage, and ground connections.

5. 5

   Check the compatibility of the program versions, settings, and calibration between the modules.

1. 1

   Inspect Wiring

   Begin by visually inspecting the wiring harness between the TR2 transmission module (located behind the driver's seat on many models) and the EXT external function module. Look for chafed wires, loose pins, or corrosion in the connectors.

2. 2

   Test CAN Bus

   Using a multimeter, test the CAN bus lines between the TR2 and EXT modules for continuity. Ensure there is no short to ground or short to power on the CAN lines.

3. 3

   Verify Power and Ground

   Measure the voltage at the power and ground pins of both the TR2 (A57-2) and EXT (A62) modules to ensure they are receiving stable voltage under load.

4. 4

   Software Update/Calibration

   Connect the CLAAS Diagnostic System (CDS). Verify that both modules are communicating on the network. If communication is intermittent, try reflashing or updating the software to ensure compatibility.

5. 5

   Module Replacement

   If the wiring, power, and grounds are all intact, and software is up to date, one of the modules has failed internally. Replace the faulty module (TR2 or EXT). Note: Replacing the TR2 'Auto 5' module requires specific CLAAS tooling (tool n° 60 05 033 249) for configuration and calibration.