British Masters champion Noren, who has three tour wins in 2016, shot to the top of the leaderboard following a 67 to move to eight under par and a two-shot lead over a chasing pack of five players.
Paraguayan Fabrizio Zanotti, who earlier landed the first hole-in-one in the tournament's 35-year history, looked as though he would grab a share of the overnight lead before he bogied 17 and 18 and settled for a 68.
Zanotti, who achieved his ace with a seven iron from 210 yards on the par-three fourth, was joined on six under by home favourite Louis Oosthuizen, who carded the low round of the day with six birdies in his 66.
South Africans George Coetzee and Jaco van Zyl (both 69s), and England's Chris Wood (69), were also tied for second.
The Race to Dubai looks as though it will go down to the wire at the season-ending DP World Tour Championship in Dubai next week after money-list leader Henrik Stenson carded a disappointing 74 in his second round for an aggregate total of one under par.
The Swede could have wrapped up the title of Europe's top golfer in 2016 with victory at Sun City and a finish outside of the top 10 for his nearest money-list rival, Danny Willett.
But both face a battle for a place near the top of the leaderboard after Willett's poor form continued with a 74 that left him on five over par.
Original source: Noren leads Nedbank Challenge