Code 231-8C00: Encoder on speed input %1 is defective
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical Encoder on speed input %1 is defective 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
[Cause of error] - There is no motor encoder signal - There is a break in the motor encoder cable - The signal amplitude of the motor encoder is missing or too small - The motor encoder is contaminated - Incorrect parameters of posEncoderResistor during use of an external Y cable [Error correction] - Check the motor encoder connection - Check the motor encoder for proper function - Check the amplitude of the motor encoder signal - Check configuration in machine parameter PosEncoderResistor. If an external Y cable is used, a 1 has to be entered in this machine parameter. - Inform your service agency
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 231-8C00 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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