Nystrom, who started on the back nine, bogeyed No. 7 and parred his last two holes on the wind-swept Arlandastad course. Kaymer (68), Walker (70) and Nystrom are at 5-under 135.
John Daly (75) missed the cut with a 147 total, going 6 over on the first six holes.
James Kingston shot his second 68 and was one stroke behind the leaders. Nick Dougherty (69), Edward Rush (68) and Jean-Baptiste Gonnet (70) were tied for fifth another shot back.
Scott Strange, who entered the tournament as the first reserve and led after an opening-round 64, slipped to a 75 and dropped into a tie for 14th.
Corey Pavin (70) shared 18th and Jeff Sluman (71) was tied for 29th.