McDowell fights back against Yang
Yang, who won their third-round clash 3 and 2 in 2011, needed only a par four to take the opening hole, and although Northern Irishman McDowell birdied the next two so did his opponent to remain one up.
The tables turned in favour of the former US Open Champion as McDowell took the fourth with a birdie and fifth with a par, but former US PGA Champion Yang birdied the par three sixth to leave matters all square.
In the first of six all-European duels, England's Justin Rose and Scot Paul Lawrie both parred the first, but Americans Hunter Mahan and Bill Haas fell one down there.
Mahan was playing Ryder Cup team-mate Zach Johnson, while Haas, winner of the Northern Trust Open on Sunday, was up against 20 year old Japanese player Ryo Ishikawa.
Rose struck first against Lawrie, the 1999 Open Championship winner bogeying the short third, while Denmark's Thomas Björn, conqueror of Tiger Woods at the same stage a year ago, instantly dropped a stroke to trail Italian Francesco Molinari.
Yang was ahead again when he birdied the seventh and McDowell's double bogey on the 476 yard ninth meant he turned two down.
Rose bogeyed to lose the fourth and his match with Lawrie remained all square after six, while 2010 winner Ian Poulter shared the first three holes with Korean Bae Sang-moon, Bjorn hit back to lead Molinari by one after four and Scot Martin Laird's opening bogey left him one down to Spaniard Alvaro Quiros.
McDowell birdied the 219 yard 12th to be only one down once more, but reaching the green in two at the long next was not enough to put him on level terms as Yang made a nine footer for a matching birdie.
Rose fell two behind with back-to-back bogeys on seven and eight, Poulter was one down after seven, Laird still one down after four and Robert Rock, in the field thanks to beating Woods and the world's top four in Abu Dhabi last month, struck first against Adam Scott, but lost the second and third.