Rickie Fowler shot an eight-under 64 to share the lead with Scottie Scheffler after the second round of the American Express in California.
Fowler completed a six-under 30 through his final nine, registering a six-foot eagle putt on the fourth and four birdies.
Scheffler birdied six of his first seven holes, finishing with an eagle and two more birdies to match Fowler's 64 and level up on 15 under.
"I feel like I've been playing pretty well, just doing a good job managing my game, giving myself a lot of looks," Scheffler told the PGA tour website.
American Andrew Landry was one shot further back, with compatriot Tony Finau on 13-under.
Scotland's Russell Knox finished the day tied for 39th at seven-under.
Fowler and Scheffler will play PGA West's Stadium Course on Saturday.
