CLAAS Id7894h / 7894h – EXT (A62) - External function module: CAN bus communication failure between EXT and WLP

The EXT (External function module) is receiving invalid information from the WLP (Working light module) for more than 5 seconds over the vehicle's CAN bus network, making the information from the WLP unavailable on the 7-pin ISO connector.

• CLAAS Axion 810 - 850
• CLAAS Axion 920 - 950
• CLAAS Axion 960
• CLAAS Arion 510 - 640
• CLAAS Arion 530 - 550 / 620 - 650
• CLAAS Jaguar

1. 1

   Check the CLAAS vehicle CAN bus network for CAN frame errors or network communication module faults

2. 2

   Check the CAN bus network communication module (BDG A103) to ensure it is transmitting properly

3. 3

   Check power and ground sources for both the WLP (A104) and EXT (A62) modules, as a blown fuse for the WLP module is a common cause

4. 4

   Inspect wiring for any short-circuits or open circuits between the WLP, the EXT, and the 7-pin ISO connector

1. 1

   Inspect the 7-Pin ISO Connector

   Check the physical 7-pin ISO connector at the rear of the tractor for dirt, corrosion, or bent pins. Clean the contacts with electrical contact cleaner.

2. 2

   Verify Fuses and Relays

   Locate the fuse box and check the specific fuses responsible for the WLP (Work light module) power supply. Replace any blown fuses.

3. 3

   Test the CAN Bus Wiring

   Using a multimeter, test the CAN High and CAN Low lines between the WLP (A104) and EXT (A62) modules for continuity. Repair any broken wires or chafed harnesses.

4. 4

   Check Module Connections

   Disconnect the wiring harnesses at both the EXT (A62) and WLP (A104) modules. Inspect for moisture or pin damage. Reconnect securely.

5. 5

   Software/Calibration Check

   If the wiring and power supplies are intact, check the compatibility of the program versions via the CLAAS Diagnostic System (CDS). The modules may require a software flash or reconfiguration.

6. 6

   Module Replacement

   If all wiring, power, and software checks pass but the EXT module still cannot communicate with the WLP, the WLP (A104) or EXT (A62) module itself has likely failed internally and must be replaced.