Code 235220: <location>TM: Frequency limit reached for signal output
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>TM: Frequency limit reached for signal output 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: OFF1 (NONE, OFF2) SERVO: OFF1 (NONE, OFF2, OFF3) VECTOR: OFF1 (NONE, OFF2, OFF3) Acknowledge: IMMEDIATELY (POWER ON) Cause: The signals output from the Terminal Module 41 (T M41) for tracks A/B have reached the limit frequency. The output signals are no longer in synchronism with the specified setpoint. SINAMICS-Alarms Diagnostics Manual (DAsl), 03/2009 Remedy: SIMOTION (p4400 = 0) operating mode: - enter a lower speed setpoint (p1155). - reduce the encoder pulse number (p0408). - if the TM41 is configured as te chnology object in SIMOTION, then this fault is generated if the A/B signals in connector X520 are short-circui ted SINAMICS (p4400 = 1) operating mode: - the fine resolution of TM41 in p0418 does not match that of the connector input that was interconnected at P4420 - the encoder position actual value r0479 interconnec ted at connector input p4420 has an excessively high actual speed
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 235220 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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