231-D400

Power down the control safely

Switch off the main control power at the cabinet. Wait at least 30 seconds for capacitors to discharge before opening the control housing.

Ensure machine emergency stop is engaged and follow lockout/tagout procedures before accessing control electronics.

Inspect HSCI cable connections

Locate the HSCI ribbon cables or shielded cables connecting the CC board (main processor board) to the SPL module rack. Check both ends for proper seating in connectors, bent pins, and cable damage. The HSCI address in the alarm indicates which SPL position to focus on.

HSCI cables are typically flat ribbon cables with keyed connectors. Note the orientation key to prevent reverse insertion during reconnection.

Reseat HSCI connections

Carefully disconnect and reconnect the HSCI cable at both the CC board and the SPL module corresponding to the HSCI address shown in %1. Ensure connectors click or seat fully with no gaps.

Use a non-conductive tool to release locking tabs if present. Clean contacts with contact cleaner if corrosion or dust is visible.

Test after reconnection

Power up the control and observe if alarm 231-D400 clears during startup. Monitor for several minutes during normal operation to ensure the watchdog error does not recur.

Access MOD → System Diagnostic → Event Log to check if communication errors are logged even when alarm doesn't trigger.

Identify the affected SPL module

Use the HSCI address from the %1 parameter to locate the physical SPL module. HSCI addresses typically correspond to slot positions in the SPL rack (consult your control's hardware manual for address mapping).

On multi-axis machines, HSCI address often correlates to axis assignments: address 0 = X-axis SPL, address 1 = Y-axis SPL, etc.

Check SPL diagnostic LEDs

Examine the LED indicators on the suspect SPL module. Normal operation shows a steady green LED. Red LED, flashing patterns, or no LED indicates module fault. Refer to the LED pattern table in the SPL module documentation.

Perform visual inspection with control powered on but do not touch components. Observe from a safe distance.

Review SPL temperature and voltage

Access Service mode → Test → Hardware Test → SPL Diagnostics. Check operating temperature and supply voltages for the module at the HSCI address. Temperatures above 70°C or voltages outside ±5% tolerance indicate problems.

Blocked ventilation or failed cooling fans often cause SPL overheating. Check airflow through the control cabinet.

Swap SPL module (if spare available)

Power down completely. Replace the suspect SPL module with a known-good spare or swap with an identical SPL from a less-critical axis. Power up and test. If alarm moves to the new location, cable or CC board is faulty. If alarm clears, SPL module is defective.

Only swap identical SPL module types. Different firmware or hardware revisions may cause additional errors. Record module serial numbers before swapping.

Order replacement SPL module

If SPL module is confirmed defective, contact Heidenhain service with the control serial number, SPL module type/part number (visible on module label), and HSCI address to order exact replacement. Firmware transfer may be required for new modules.

Keep the defective module for potential warranty analysis. Heidenhain may request return for failure investigation.

Verify multiple SPL communication status

Access Test → System Information → HSCI Status to view communication state of all connected SPL modules. If multiple HSCI addresses show errors or timeouts (not just %1), the CC board HSCI interface is likely faulty rather than individual SPL modules.

Single HSCI address error points to SPL or cable; multiple simultaneous errors suggest CC board or power supply issues.