MAS OSC FLT fault in abb acs800 drive indicates an issue with the communication oscillator signal on the fieldbus. This signal is a toggling bit used to detect communication errors and ensure the drive and the master controller are actively communicating

• Ensure all fieldbus cables are securely connected to both the master controller and the drive.
• Verify the wiring according to the fieldbus standard.
• Inspect the cables for any signs of damage.