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Check Drive Terminal Connections

Verify 24V enable signal is present at SINAMICS drive X122 connector pins 1-2 (Enable) using multimeter. Signal should read 24VDC when system is ready.

Ensure proper lockout/tagout procedures before checking electrical connections

Verify Enable Chain Wiring

Trace enable signal from PLC output through emergency stop circuits, safety relays, and any intermediate contactors to drive enable input. Check for loose connections or blown fuses.

Use SINUMERIK Operate diagnostics screen to monitor PLC I/O status in real-time

Test Enable Signal Continuity

With system powered down, use ohmmeter to verify continuity through entire enable chain from PLC output terminal to drive input terminal.

Document any intermediate relay contacts or safety devices in the enable path for future reference

Check PLC Program Logic

Access SINUMERIK Operate > Diagnostics > PLC and verify that the axis enable output (typically DB31.DBX0.0 for axis 1) is being set TRUE by PLC program logic.

Use PLC variable monitoring to watch enable bit status in real-time during troubleshooting

Verify Safety Interlock Status

Check all safety-related PLC inputs including emergency stops, guard switches, and safety PLC outputs that feed into axis enable logic. Navigate to Diagnostics > Machine > Safety to view safety signal status.

Never bypass safety interlocks - resolve the underlying safety condition instead

Monitor Cyclic Telegram

Use SINUMERIK Operate > Diagnostics > Drive to view real-time status of control word bits being sent to SINAMICS drive. Verify bit 2 (Controller Enable) is being set.

Compare control word values with SINAMICS manual to decode all active enable conditions

Check Enable Input Parameters

Access SINAMICS STARTER or SINUMERIK Operate > Commissioning > Drive and verify P8401 (Enable input polarity) and P8402 (Enable monitoring) are correctly configured for your hardware setup.

P8401=0 for normally open contacts, P8401=1 for normally closed - match your actual wiring

Verify Enable Source Selection

Check parameter P848x series to ensure enable sources are properly configured. P8480 should typically include both hardware enable (bit 0) and PLC enable (bit 1) sources.

Use SINAMICS parameter backup before making changes to enable quick restoration if needed

Review Enable Monitoring Time

Verify P8411 (Enable monitoring time) is set appropriately for your system response time. Too short may cause nuisance alarms, too long delays fault detection.

Consult machine documentation before changing timing parameters as this affects safety response

Check Communication Status

Navigate to SINUMERIK Operate > Diagnostics > Hardware and verify PROFINET/PROFIBUS communication status to affected drive shows green/OK status without timeout errors.

Look for intermittent communication errors in the diagnostic buffer that may indicate cable issues

Verify Network Configuration

Check PROFINET IP addresses and device names match between HW Config and actual drive settings. Verify no duplicate IP addresses exist on network.

Document current network settings before making any changes to avoid communication loss

Test Physical Network Connection

Check PROFINET cable connections at both NC and drive ends. Verify cable integrity and proper termination. Use network diagnostic tools to test connectivity.

Swap network cables with known good axis to isolate cable vs. hardware issues