Code 26123: [Channel %1: ] Axis %2, $AA_ESR_ENABLE = 1 should be set, but MD37500 $MA_ESR_REACTION = 0
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical [Channel %1: ] Axis %2, $AA_ESR_ENABLE = 1 should be set, but MD37500 $MA_ESR_REACTION = 0 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 %2 = Axis, spindle Definitions: $AA_ESR_ENABLE[axis] = 1 should only be set on axes with MD37500 $MA_ESR_REACTION[Achse] > 0. The following example brings about the alarm: N100 $MA_ESR_REACTION[AX1] = 21 N110 $AA_ESR_ENABLE[AX1] = 1 N120 NEWCONF because MD37500 $MA_ESR_REACTION[AX1] = 21 will become known to the NCK at the time of N120 NEWCONF. Correct would be: N100 $MA_ESR_REACTION[AX1] = 21 N110 NEWCONF N120 $AA_ESR_ENABLE[AX1] = 1 Reaction: Alarm display. Remedy: Before setting $AA_ESR_ENABLE[axis] = 1, MD37500 $MA_ESR_REACTION[axis] > 0 must be set. When setting MD37500 $MA_ESR_REACTION[axis] in th e parts program, e.g. NEWCONF must be called before $AA_ESR_ENABLE[axis]. Alarm can be suppressed via MD11415 $MN_SUPPRESS_ALARM_MASK_2 bit 6 = 1. Program Continuation: Clear alarm with the Delete key or NC START.
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 26123 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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