Code 233117: <location>Encoder 3: Inversion error signals A and B and R
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>Encoder 3: Inversion error signals A and B and R 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: Drive object: All objects Reaction: A_INFEED: NONE SERVO: OFF1 (IASC/DCBRAKE, NONE, OFF2, OFF3) VECTOR: OFF1 (IASC/DCBRAKE, NONE, OFF2, OFF3) Acknowledge: IMMEDIATELY Cause: For a square-wave signal encoder (TTL. bipolar. double ended) the A* and B* and R* signals are not inverted with respect to signals A and B and R. Note: For CU310, CUA32, D410, SMC30 (only Order No. 6SL3055-0AA00-5CA0 and 6SL3055-0AA005CA1), the following applies: A squarewave encoder without trac k R is used and the track monito ring (p0405.2 = 1) is activated. Remedy: - check the setting of p0405: p0405.2 = 1 is only possible if the encoder is connected at X520. - check the encoder/cable: Does the encoder suppl y TTL signals and the associated inverted signals? Note: For a squarewave encoder without track R, the foll owing jumpers must be set at the encoder connection: - pin 10 (reference signal R) <--> pin 7 (encoder power supply, ground) - pin 11 (reference signal R inverted) <--> pin 4 (encoder power supply)
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 233117 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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