Code 208700: <location>CBC: Communications error
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>CBC: Communications error alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Message value: %1 Drive object: CU_LINK, CU_S, HUB, SERVO, TB30, TM15, TM15DI_DO, TM17, TM31, TM41, TM54F_MA, TM54F_SL, VECTOR Reaction: A_INFEED: NONE SERVO: OFF3 (NONE, OFF1, OFF2) VECTOR: OFF3 (NONE, OFF1, OFF2) Acknowledge: IMMEDIATELY Cause: A CAN communications error has occurred. Fault value (r0949, interpret decimal): 1: The error counter for the send telegrams has exceeded the BUS OFF value 255. The bus disables the CAN controller. - bus cable interrupted. - bus cable not connected. - incorrect baud rate. - incorrect bit timing. 2: The master no longer interrogated the CAN node status longer than for its "life time". The "life time" is obtained from the "guard time" (p8604[0]) mu ltiplied by the "life time factor" (p8604[1]). - bus cable interrupted. - bus cable not connected. - incorrect baud rate. - incorrect bit timing. - master fault. Note: The fault response can be se t as required using p8641. See also: p8604 (CBC node guarding), p8641 (CBC abort connection option code) SINAMICS-Alarms Diagnostics Manual (DAsl), 03/2009 Remedy: - check the bus cable - check the baud rate (p8622). - check the bit timing (p8623). - check the master. See also: p8622 (CBC baud rate), p8623 (CBC bit timing selection)
Source: SINUMERIK 840D sl / 840Di sl / SINAMICS S120 Diagnostics Manual (DAsl, 03/2009)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINUMERIK 840D CNC Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 208700 on the SINUMERIK 840D CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4014 Siemens SINUMERIK 840D CNC codes.
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