AH500 Module Manual 10-64 Error code Description How to deal with extension rack connection fails. 3. Check if the bus communication cable length exceeds the maximum transmission distance. (Refer to section 10.3.3. The system may no longer keep stable if the maximum distance is exceeded.) 4. Check if all modules on the rack are normal. 5. Check if the extension rack connected to AHRTU-DNET is connected normally.