CLAAS Id788Bh / 788Bh – EXT (A62): CAN bus communication timeout related to vehicle speed

The EXT external function module has not received theoretical speed information for over 5 seconds via the CAN bus. As a result, the theoretical speed information is not available on the 7-pin ISO connector.

• CLAAS Axion 800 Series
• Axion 810
• Axion 850
• CLAAS Axion 900 Series
• Axion 920
• Axion 950
• CLAAS Arion 500 / 600 Series
• Arion 510
• Arion 640

1. 1

   Verify the 7-pin ISO Connector for physical damage, corrosion, or pushed-out pins that might be shorting the CAN network.

2. 2

   Check the CLAAS Vehicle CAN Bus Network for continuity, proper terminating resistance (typically 60 ohms across CAN High and CAN Low), and ensure there are no short-circuits to ground or 12V.

3. 3

   Inspect associated modules (BDG A103, DBD A101, TR3 A143, and EXT A62) for proper status and secure connections.

4. 4

   Check power and ground sources (fuses, power supply, and ground) for the EXT module and the CAN bus network.

1. 1

   Visual Inspection

   Inspect the wiring harnesses linking the EXT (A62), BDG (A103), and DBD (A101) modules. Look for chafed wires, especially near articulation points or where harnesses pass through the cab floor.

2. 2

   Connector Maintenance

   Disconnect the 7-pin ISO connector and the harness connectors at the EXT module. Clean the contacts with electrical contact cleaner and ensure no moisture has intruded.

3. 3

   Harness Testing

   Using a multimeter, perform a continuity test on the CAN lines between the transmission module (which generates the speed data), the BDG gateway, and the EXT module. Repair any open circuits.

4. 4

   Software/Calibration Check

   If the wiring is intact, connect the CLAAS diagnostic tool (CDS) to check for compatibility of program versions, settings, and calibration across the modules. Sometimes a module update or reconfiguration is required if a module has lost its parameterization.

5. 5

   Module Replacement

   If all wiring, power, grounds, and software configurations are correct, the fault lies within the hardware of one of the modules failing to transmit or receive the CAN frame. Replace the faulty component (most likely the EXT A62 module or the BDG A103 gateway) as dictated by the CDS test and measurement files.