Cause : UNDERLOAD comes when the motor is operating below its normal load conditions. This can happen due to various reasons such as a reduced load demand, mechanical issues in the driven equipment, or an actual reduction in the motor's load.

The code FF6A in your ABB ACS800 drive indicates a fault related to an underload condition on the motor. This means the motor is not consuming the expected amount of power from the drive.

1. Check for problem in driven equipment.
2. Check Fault Function parameters.