North End keeper Wayne Henderson was kept busy before the break and Shaun Newton blasted over for Leicester.
Iain Hume shot high and wide when well placed for Leicester and also hit the post with a free-kick before Newton set up Johansson to slot home the winner.
Leicester manager Nigel Worthington:
"We've been building to that. We're capable of doing it and overall we got our just rewards. We stuck at it and it was an excellent three points.
"It was a battling performance with a never-say-die attitude, which is what I like to look for in teams and players.
"We've worked on that over the last 10 days and we're starting to get to grips with what we're looking for."
Preston: Henderson, Alexander, St. Ledger, Chilvers, Hill (Whaley 78), Sedgwick (Agyemang 82), Soley, Davidson, Pugh, Nugent, Ormerod (Ricketts 72).
Subs Not Used: Lonergan, Wilson.
Booked: Chilvers, Nugent.
Leicester: Logan, Stearman, Kisnorbo, McAuley (Horsfield 67), Johansson, Newton, Hughes, Wesolowski, Mattock, Fryatt (Cadamarteri 61), Hume.
Subs Not Used: Henderson, Maybury, Hammond.
Booked: Hume, Newton, Kisnorbo.
Goals: Johansson 90.
Ref: C Oliver (Northumberland).