Code 231-8A90: Safety module %1
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical Safety module %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] - Not a safety-oriented control: - The drive cannot be switched on because the safety module is locked - Switch-off of the drive through removal of the external drive enabling at the input of the safety module - Safety module is defective (exchange) - Safety-oriented control: - Drive cannot be switched on because of the operating status of the machine - Drive was switched off because of a change to an illegal operating status of the machine [Error correction] - Inform your service agency - Safety module is connected only to CC: - Switch the external drive enabling over the corresponding input at the safety module (apply 24 V) - Safety modules are connected at MC and CC: - All drives: - Check the function of the protective door contact - Cancel the emergency stop - Only spindle drive: - Check the tool holder (closing) - Check the permissive key - Check the position of the detachable-key switch - Exchange the safety module(s)
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 231-8A90 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.
Have a better solution?
Help the industrial community by sharing your repair experience for code 231-8A90.
Need a searchable reference for more Heidenhain TNC Series CNC manuals?
We structure equipment manuals into searchable code, title, cause, solution, safety note, and source-reference data. Send a PDF and example searched codes when you need public pages, private search, or structured exports.
Space reserved for Google AdSense / Industrial Affiliate Links
Monetization target for 2026