CLAAS Id78B6h / 78B6h (846) – 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 (CLAAS Sequence Management) sequence

As a direct system response to this communication failure, the 4-wheel drive is disconnected.

• Axion 800
• Axion 810
• Axion 850
• Arion 410
• Arion 430
• Arion 510
• Arion 530
• Arion 550
• Arion 620
• Arion 640
• Arion 650

1. 1

   Check the TR2 transmission module (A57-2) and the external function module EXT (A62) for basic functionality

2. 2

   Check the CLAAS vehicle CAN bus network for communication integrity

3. 3

   Check connectors and harness continuity linking the TR2 module, the EXT module, and the CAN bus

4. 4

   Check for short-circuits or open circuits in the wiring

5. 5

   Check the sources of energy: Verify all relevant fuses, power supply voltages, and ground connections to both the A57-2 and A62 modules

6. 6

   Check software compatibility: Ensure the program versions, settings, and calibrations of the modules are compatible and up to date

1. 1

   Power Cycle & Clear

   Restart the tractor and attempt to relaunch the CSM sequence to see if the communication loss was a momentary glitch.

2. 2

   Visual & Physical Inspection

   Locate the TR2 (A57-2) transmission module (typically located behind the driver's seat) and the EXT (A62) module. Inspect the 42-terminal connectors and wiring harnesses for corrosion, backed-out pins, or moisture intrusion.

3. 3

   Electrical Testing

   Using a multimeter, test the CAN High and CAN Low lines between the TR2 and EXT modules for continuity. Verify that the CAN bus terminating resistors are intact (typically 60 ohms across the network).

4. 4

   Power & Ground Verification

   Test the power supply and ground pins at both modules under load to ensure they are not dropping out during operation.

5. 5

   Software/Calibration

   If wiring is intact, connect the CLAAS Diagnostic System (CDS) to verify if the modules require a software flash or recalibration.

6. 6

   Module Replacement

   If all wiring, power, ground, and software checks pass but the communication loss persists, replace the faulty component (either the TR2 transmission module or the EXT module) as indicated by the diagnostic tool.