Code 16938: [Channel %1: ] Action %2<ALNX> aborted due to active gear change
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical [Channel %1: ] Action %2<ALNX> aborted due to active gear change 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
Parameters: %1 = Channel ID %2 = Action number/action name Definitions: Reorganization events are, among others, subprogr am abort, delete distance-to- go and interrupts, axis exchange, exiting the correction state. Thes e events wait for the end of a gear change. However, the maximum waiting period has elapsed. Reaction: NC Start disable in this channel. Interface signals are set. Alarm display. NC Stop on alarm. Remedy: Program must be aborted with Reset and, if necessary, MD10192 $MN_GEAR_CHANGE_WAIT_TIME must be increased. Program Continuation: Clear alarm with the RESET key. Restart part program
Source: SINUMERIK 840D sl / 840Di sl / SINAMICS S120 Diagnostics Manual (DAsl, 03/2009)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINUMERIK 840D CNC Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 16938 on the SINUMERIK 840D CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4014 Siemens SINUMERIK 840D CNC codes.
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