Code 231-9550: EnDat2.2 - FS single-encoder system incorrectly
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical EnDat2.2 - FS single-encoder system incorrectly 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
configured %1 [Cause of error] It was configured so that both only the EnDat 2.2 position encoder and only the EnDat 2.2 shaft speed encoder are to be used for functional safety. This is not possible. [Error correction] - Check the entry in Machine Parameter CfgAxisSafety-encoderForSafety: It must either be "speedAndPosEncoder", "speedEncoder" or "posEncoder". - Special settings for single-encoder systems with EnDat 2.2 FS encoders: Set "posEncoder" if only the position encoder is to be used for functional safety or set "speedEncoder" if only the shaft speed encoder is to be used for functional safety - Standard setting: Set "speedAndPosEncoder" if you want to configure a normal dual-encoder system or if the affected axis is run in functional safety with only one encoder (single-encoder safety).
Source: HEIDENHAIN NC Error Messages — TNC7/640/620/320/128, CNC PILOT 640, MANUALplus 620 (10/2023)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Heidenhain TNC Series CNC Alarms
Heidenhain controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 231-9550 on the TNC Series CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Heidenhain's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4497 Heidenhain TNC Series CNC codes.
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