CLAAS Id78D8h / 78D8h – EXT (A62) - External Function Module: CAN Speed Message Not Received or Invalid

Communication or sensor data failure regarding the vehicle's speed. Specifically, the CAN "Speed" message is either not being received by the external function module, or the value being received is invalid.

• CLAAS Axion 800 Series (e.g., Axion 810, 850)
• CLAAS Axion 900 Series (e.g., Axion 920, 950)
• CLAAS Arion 500 / 600 Series (e.g., Arion 510, 640)

1. 1

   Check the Speed Sensor: Verify the operation of the primary speed sensor (GPS, radar sensor, or wheel speed sensors).

2. 2

   Check the DBD (A101) Dashboard: Ensure the dashboard is properly sending the speed information to the CAN bus.

3. 3

   Check the BDG (A103) Module: Verify the network communication module is correctly relaying the CAN messages to the CLAAS vehicle CAN bus.

4. 4

   Wiring & Electrical Checks: Check the connectors and continuity of the harnesses linking the speed sensor, DBD (A101), BDG (A103), and EXT (A62) modules. Check for any short-circuits or open circuits. Check the sources of energy (fuses, power supply, and ground) for the involved modules.

5. 5

   Software Checks: Check the compatibility of program versions, settings, and calibration across the modules.

1. 1

   Visual Inspection

   Inspect the physical condition of the speed sensor (radar under the cab, GPS receiver on the roof, or inductive wheel sensors) for damage, mud/debris blockage, or disconnected wires.

2. 2

   Harness Testing

   Using a multimeter, test the wiring harness between the speed sensor and the DBD (A101) dashboard for continuity and shorts to ground. Repair any damaged wiring.

3. 3

   Module Power/Ground Test

   Verify that the EXT (A62), DBD (A101), and BDG (A103) modules are receiving proper voltage and have clean ground connections. Check the corresponding fuses in the cab fuse panel.

4. 4

   Diagnostic Tool Verification

   Connect the CLAAS diagnostic tool (CDS) to monitor live data. Check if the DBD (A101) is registering a speed value. If the dashboard sees the speed but the EXT (A62) module does not, the issue lies in the CAN bus wiring or the BDG (A103) gateway module.

5. 5

   Component Replacement

   If a sensor fails resistance/signal testing, or if a module fails to communicate on the CAN bus despite good power/ground/wiring, replace the faulty component and recalibrate the system.