Cause: Safety function module error comes when communication interruption with Safety function module or internal error of the Safety function module.

"inFi" Internal Error 18 fault in Schneider ATV950 drive indicate "Safety function module error". This means an issue with a component or process responsible for ensuring the safe operation of a system.

1. Replace the option module.
2. Inspect the safety module for physical damage or signs of malfunction.
3. Check the connections and wiring for any issues.
4. Test sensors and actuators connected to the module.