The result was a one-stroke lead for the Swedish-born player Saturday through three rounds of the Fry's Electronics Open.
Mark Hensby, playing in the same group, shared the lead until twice hitting into sand traps en route to a bogey on the par-4 18th.
With temperatures reaching into the low 90s, Pettersson shot a 6-under 64 on Saturday, tied for the best round of the day, and was at 13-under 197 in the Fall Series event on the 7,125-yard Raptor course at Grayhawk Golf Club.
'I played nice,' Pettersson said. 'I only missed two greens and didn't give myself any real opportunities to make bogeys. I played steady, and I putted pretty good, too.'
Hensby, with a 68, fell into a tie with Canadian Mark Weir at 12-under 198. Weir, the 2003 Masters champion who beat Tiger Woods in the Presidents Cup three weeks ago, followed Friday's 64 with a 65.
'For the most part, I've put it on the smart side of the hole this week,' Weir said. 'That's what you have to do around here. The greens are very difficult, so you have to put it on the right spots.'
Jarrod Lyle also shot a 64 and was tied with second-round leader Ryan Moore (71), two back at 10-under 200. Moore, who began the day with a three-stroke lead, struggled with his putting and had bogeys on two of the final three holes.
Justin Leonard, Ben Crane and Daisuke Maruyama were three back at 10-under 201.
Pettersson, who moved from Sweden to North Carolina at age 15, felt comfortable with the Bermuda grass greens.
Phoenix-area courses have Bermuda grass in the scorching summer but are overseeded with rye grass in the fall.
'Obviously they have a lot of grain,' Pettersson said, 'but you can see where the grain is going.'
Pettersson is playing his 29th tournament of the season and plans to participate in the remain two Fall Series events. He entered the week 39th on the money list at $1.79 million.
'I'm still trying to get in the top 30,' he said.
Pettersson has twice won on the TOUR -- the 2006 Memorial and 2005 Chrysler Championship.
After three days of calm, gorgeous conditions, wind of 15 to 25 mph is forecast for Sunday.
'If it stays the same, you've got to play aggressive and just the way we have been and the score will be low,' Pettersson said, 'but if it blows 30 (mph), I mean, everything goes out the window.'
Obviously perturbed by his final bogey, the Australian Hensby -- who lives in nearby Mesa -- left the course without talking to reporters. He entered the tournament 151st on the money list. He had the best round of the week at 61 on Friday.
The field was the strongest of the seven Fall Series events, but several of the bigger names, including Phil Mickelson, missed the cut Friday. With an overall purse of $5 million, $900,000 for the winner, the tournament is an opportunity for players such as Hensby to scramble into the top 125 on the money list to preserve their PGA TOUR cards for next year.
Sean O'Hair was tied for the lead at 12 under before his tee shot went left into the water on the 211-yard, par-3 15th. He wound up with a double bogey, then bogeyed the 16th.
O'Hair ended the day at 8-under 200, tied with Billy Mayfair, last week's winner George McNeill, Nick Watney and Kent Jones.
Mayfair, a local favorite born and raised in Phoenix, shot into contention with birdies on five of his first 10 holes to go to 11 under but faltered with four bogeys and a birdie on the final six.