Code 231-8C90: Amplitude too high at position encoder %1
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical Amplitude too high at position encoder %1 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] - The amplitude of the position encoder signal is too high or the signal for contamination is active - Noise on the encoder signal - Short circuit in the encoder cable - Encoder signal amplitude too high - Incorrect values in the machine parameter posEncoderResistor [Error correction] - Check the encoder connection (ground connection) - Check the encoder - Check configuration in machine parameter posEncoderResistor. If a position encoder is used (no external Y cable), a 0 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 231-8C90 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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