After a flat and tired performance in the first half, Jamie Vardy – who had previously been anonymous in terms of chances – showed his clinical ability in the box to fire the visitors ahead after 66 minutes.
He then sealed the victory in stoppage time when he rounded the goalkeeper to send the travelling fans into hysterics.
The league leaders move onto 72 points with five games remaining and they need just three more wins to seal the title. Ranieri named an unchanged side for the trip to Wearside to face Sam Allardyce’s relegation battlers.
The identity of his team has remained the same for the majority of the season and that is one of the contributors to their success to date. Wes Morgan had the best chance of the first half when he met Christian Fuchs’ corner, glancing from the near post across the face of goal.
City were appealing for a penalty before the interval as Shinji Okazaki was caught by DeAndre Yedlin in mid-air. Referee Anthony Taylor waved away appeals and the final action of the half saw Kasper Schmeichel produce a stunning save to deny Fabio Borini’s deflected shot. Leicester began to liven up in the second period and it took them 21 minutes to open the scoring.
It came through yet another pacey counter attack. Danny Drinkwater’s long ball over the top was met by Vardy, who coolly converted past Vito Mannone from a tight angle.
Sunderland could have been back on level terms in the closing stages of the game as Jack Rodwell squandered a big opportunity – blasting a six-yard effort over the crossbar.
As the league leaders headed for a fifth 1-0 win in a row, Vardy rounded the goalkeeper in added time to roll the ball into an empty net for his 21st goal of the campaign. Before Spurs’ home match with Manchester United, the 2-0 result saw Leicester go ten points clear in an incredible campaign for the East Midlands club.