Jee Young Lee posted a 65 to move into second place at minus-11. Four-time LPGA winner Hee-Won Han (64) and Kraft Nabisco Championship winner Karrie Webb share third place at 10-under-par 134.
Sorenstam, whose lone win this year was at the MasterCard Classic in March, started on the back nine and dropped a shot on the par-4 12th. She got that stroke back with her second birdie in two days on the par-4 14th.
The Swede moved to 7 under as she birdied the 17th, from 3 feet out, for the second time in two days.
Sorenstam carded her next birdie on the second as she sank a 10-footer. After four straights pars, the women's world No. 1 birdied the seventh, then parred eight and nine to finish three back.
'I thought I played well today. I didn't score as well, but I had a lot of chances,' Sorenstam said. 'I am very happy with my game. It was windier and it was tricky. The wind was swirling quite a bit. It was tough with the club selection today.'
Yim started on the front nine Friday at Eagle's Landing Country Club. She carded her first birdie on the second, but gave that shot back with a three-putt bogey on No. 5.
The 22-year-old eagled the par-5 sixth to get to 6 under. Yim poured in back-to-back birdie putts from the eighth. She moved to minus-9 with a 15-foot birdie putt at the 12th.
Yim came right back with a birdie on the 13th and made it three in a row as she also birdied 14. The Korean parred her next three holes before a birdie at the last secured her the overnight lead.
'I had just one miss, the bogey, but it was a very, very good day,' said Yim. 'My shots and my putts, everything was very good. My irons were very good, a few shots I was really close to the pin. My putting is very good.'
Lee opened with three straight pars. She then reeled off five birdies in a six-hole span to jump to 9 under.
The 20-year-old tripped to her lone bogey on the 11th. Lee quickly recovered that stroke with a birdie on No. 13. She birdied each of the last two holes to get within one of her fellow Korean.
Patricia Meunier-Lebouc, Brandie Burton, Beth Daniel, Natalie Gulbis and Karine Icher share seventh place at eight-under-par 136. Julieta Granada, Juli Inkster, Jeong Jang and Meena Lee are one stroke further back at minus- seven.
Both first-round leaders struggled on Friday. Maria Hjorth posted a 1-over 73 to slide into a tie for 16th at minus-6. Cristie Kerr struggled badly as she posted a 3-over 75 to tumble into a tie for 35th at 4-under-par 140.
The cut line fell at 1-under-par 143 with 79 players moving on to the weekend. Among those who missed the cut were Laura Diaz (144), as well as Meg Mallon, Grace Park and Rosie Jones, who were each 1-over-par 145.