Code 231-C440: PWM frequency %1 incorrect
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical PWM frequency %1 incorrect 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] - PWM frequency within a control group is incorrect [Error correction] - Inform your service agency - Check configuration data (PWM frequency) - PWM frequency > 5000 Hz only with suitable hardware and only with PWM outputs X51, X52, X57 and X58. - PWM frequency <= 5000Hz must be identical within the control groups. - PWM frequency > 3200 Hz
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-C440 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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