Having suds in the dishwasher is mostly due to using the wrong detergent, 

Use only the special dishwasher detergent to avoid suds. If this occurs, open the dishwasher and let the suds evaporate. Add 3.5L of cold water to the bottom of the dishwasher.

Close the dishwasher door, then select any cycle. Initially, the dishwasher will drain out the water. Open the door after the draining stage is complete and check if the suds have disappeared.

Repeat if necessary