Code 233126: <location>Encoder 3: Amplitude AB too high
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>Encoder 3: Amplitude AB too high 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
Message value: Amplitude: %1, Angle: %2 Drive object: All objects Reaction: A_INFEED: NONE SERVO: OFF1 (IASC/DCBRAKE, NONE, OFF2, OFF3, STOP1, STOP2) VECTOR: OFF1 (IASC/DCBRAKE, NONE, OFF2, OFF3, STOP1, STOP2) Acknowledge: PULSE INHIBIT Cause: The amplitude (root of A^2 + B^2 or |A| + |B|) for encoder 3 exceeds the permissible tolerance. Fault value (r0949, interpret hexadecimal): yyyyxxxx hex: yyyy = Angle xxxx = Amplitude, i.e. root from A^2 + B^2 (16 bits without sign) The nominal signal level of the encoder must lie in the range 375 mV to 600 mV (500 mV -25/+20 %). The response threshold for (|A| + |B|) is > 1120 mV or the root of (A^2 + B^2) > 955 mV. A signal level of 500 mV peak value corresponds to the numerical value of 299A hex = 10650 dec. The angle 0... FFFF hex corresponds to 0... 360 degrees of the fine position. Zero degrees is at the negative zero crossover of track B. Note: The analog values of the amplitude error are not measured at the same time with the hardware fault output by the sensor module. Remedy: - check that the encoder cables and shielding are routed in compliance with EMC. - replace the encoder or encoder cable.
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 233126 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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