Mattias Ekholm circled out of the offensive zone before skating back in with speed on the right side and dropped a pass to Johansen. Ekholm then headed to the net, and Johansen's centering pass deflected off Kahkonen into the net.
"We're wearing them down throughout the game, spent a lot of time in the [offensive] zone and we figured we'd get a break if we kept going," Johansen said. "Got a lucky bounce there at the end, and we'll take it."
Juuse Saros made 25 saves for his fourth shutout of the season for the Predators (42-26-5), who swept the season series 3-0-0 (Sharks 0-2-1).
Nashville remained one point ahead of the Dallas Stars for the first wild card into the Stanley Cup Playoffs from the Western Conference. Dallas defeated the Tampa Bay Lightning 1-0 on Tuesday.
"[Saros] had some timely saves tonight, for sure," Nashville coach John Hynes said. "That's what happens sometimes where you're pressing a little bit to try to be able to score, and that's an area where we can do a little better job. [Saros] came up with some key saves at key times for us. That's what makes him the quality goaltender that he is. He gives you a chance every night."
Kaapo Kahkonen made 40 saves for the Sharks (29-33-10), who have lost seven straight (0-5-2).
"Good road game," Kahkonen said. "We battled hard and we didn't step back. We did a lot of good things. We were in the game all game, just tough result again. But I think a lot of good things for being on the road and playing a good team.
"The guys did a good job blocking shots and boxing out. That's what you've got to do this time of year, especially moving forward. Those things are huge and eventually will lead to success."