A121 Autotuning failed alarm in ABB DCS800 drive indicates that the automatic tuning process has failed. Autotuning is a feature that allows the drive to automatically optimize its control parameters for optimal performance.

• When this process fails, it can lead to suboptimal performance, instability, or even damage to the drive or connected equipment.
• Verify that the motor is not overloaded.
• Inspect the mechanical coupling and load for any issues.
• Review the motor parameter settings, such as rated current, voltage, and inertia.
• Ensure that these settings are correct and appropriate for the motor and load.