Heidenhain TNC 620 Error Code 401

Heidenhain CNC Major PLC

Model: TNC 620 | Code: 401

Applicable Systems
TNC 620

Symptoms

PLC stop. The PLC has stopped running. All PLC-controlled functions are suspended.

Possible Causes

  • PLC program fatal error
  • PLC watchdog timeout
  • PLC hardware fault
  • PLC stop command from user or NC

Troubleshooting Steps

  1. Step 1: Check the equipment status and fault indicators to confirm the active fault code
    Fault indicator or HMI displays code 401 as active
  2. Step 2: Verify all electrical connections, wiring harnesses, and connector seating
    All connections secure, no corrosion, loose pins, or damaged wires
  3. Step 3: Check the system diagnostic buffer or event log for detailed fault information
    Diagnostic buffer shows the specific fault cause and timestamp
  4. Step 4: Verify power supply stability and environmental conditions
    Power supply stable, environment within specifications
  5. Step 5: Restart the equipment or power-cycle the control system
    Equipment restarts and enters normal operating state
  6. Step 6: Contact manufacturer support if the fault persists after all checks
    Support provides specific troubleshooting guidance

How to Reset

To reset: 1) Identify and fix the root cause described in the fault symptoms. 2) Press RESET on the HMI or controller, or power-cycle the equipment. 3) If the fault recurs, contact manufacturer service. Caution: Document the fault code and context before resetting.

Frequently Asked Questions

  • Q: What does fault code 401 mean on the Heidenhain TNC 620?

    Fault 401 on the Heidenhain TNC 620 indicates: PLC stop. The PLC has stopped running. All PLC-controlled functions are suspended. Refer to the equipment manual and manufacturer support for specific troubleshooting steps.

  • Q: Can I continue operating the equipment with fault 401 active?

    No. The equipment has detected a fault condition and has taken protective action (typically stopping or derating). Continuing to operate without fixing the root cause may cause further damage. Always investigate and fix the fault before resuming operation.

Related Heidenhain Fault Codes

Source: Heidenhain TNC 620 Operating Manual, Heidenhain Documentation

Category: CNC