Unless you are a professional deck cleaner with lots of experience with pressure washing, don’t try it on your wood deck.
Wood is soft, and pressure-washing can damage it. At a minimum, it will ruin the finish on your deck. But more likely, it will cause your deck to splinter and even to erode.
A better kind of power wash for your deck: elbow grease. Clean your deck using a stiff brush and a cleaner formulated for use on wood.
If your deck is already damaged from pressure-washing, rent a big electric sander and smooth the boards back out before sealing it with a water-repellent finish. Always sand in the direction of the grain.