Code 16748: [Channel %1: ] Block %2 spindle %3 gear stage %4 expected
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical [Channel %1: ] Block %2 spindle %3 gear stage %4 expected 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 number %2 = Block number, label %3 = Spindle number %4 = Gear stage Definitions: G331 activates the second gear stage data block for tapping. The programmed speed (S) of the master spindle lies outside the speed range of the active gear stage in the current traversing block. The gear stage cannot be changed in the traversing block. The gear stage appropriate for the speed must be loaded prior to the traversing block. Reaction: Correction block is reorganized. Interface signals are set. Alarm display. Remedy: Procedure for automatically engaging the suitable gear stage prior to thread cutting: * Program the spindle speed (S) in a G331 block wit hout axis motions and prior to thread cutting, e.g. G331 S1000. * Activate M40 for the spindle. Program Continuation: Clear alarm with NC ST ART or RESET key and continue the 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 16748 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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