Code 208758: <location>CBC: Number of PDO channels too low
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>CBC: Number of PDO channels too low 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: Drive object: A_INF, B_INF, CU_LINK, CU_S, HUB, S_INF, SERVO, TB30, TM15, TM15DI_DO, TM17, TM31, TM41, TM54F_MA, TM54F_SL, VECTOR Reaction: NONE Acknowledge: NONE Cause: The number of PDO channels in p8740 has either been set to 0 or too low. See also: p8740 (CBC channel assignment) Remedy: The number of channels set in p8740 must be greater than or equal to the number of PDOs. There are 2 possibilities: Increase the number of channels in p8740 and confirm the selection using p8741. Reduce the number of PDOs by setting the COB-ID to invalid. See also: p8740 (CBC channel assignment), p8741 (C BC PDO configuration acknowledgement) SINAMICS-Alarms
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 208758 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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