Fowler followed up his record-breaking first round 62 with a rollercoaster 68 that mixed eight birdies with six bogeys to sit 10-under par after 36 holes, one clear of fellow American Wyndham Clark (29).
"The birdies are out there if you put yourself in the right position," said Fowler, whose 18 birdies through the first 36 holes is a U.S. Open record.
"But as you can see, bogeys are very easy to make."
He proved Thursday's heroics were no fluke when he opened his second round with three straight birdies and managed to get himself out of trouble with superb putting before signing a colourful scorecard that included just four pars.
Fowler, who had fallen off the golf map in recent years, has thrilled fans with his sensational play this week, leading many to hope the Southern Californian can capture his first major title in LA.
"There has been a lot of adversity in the last three years," Fowler said.
"It's been a while since I've felt this good in a tournament, let alone a major. It's going to be a challenge, but I'm definitely looking forward to it."
Fowler will not rest easy with Clark on his heels, Rory McIlroy (34) and Xander Schauffele (29) two back, Harris English (33) three off the pace and world number one Scottie Scheffler (26) and 2016 champion Dustin Johnson (38) also in pursuit.
Schauffele shared history with his friend Fowler by carding a 62 of his own on Thursday, but a stretch of three bogeys on the back nine threatened to swing momentum against him.
He bounced back, though, to birdie the final two holes and finish with an even par 70.
"It was big, just to keep myself in touch," Schauffele said of his finish.
"Four back wouldn't have been out of this world, but I was just playing too good a golf in my head to let that round get away from me."
In the morning wave, Clark drilled a monster 44-foot putt on the par-four 16th before capturing his fourth birdie of the day on his penultimate hole to sign for a second round 67.
"Fairways are pretty wide out here so you can just bomb it," said Clark, who emerged from a stacked field to win at Quail Hollow last month for his first PGA Tour victory.
McIlroy finishes strong
World number three McIlroy got hot late and birdied four of his last five holes, including the par-three ninth, where he narrowly missed a hole-in-one to keep his hopes of ending his nearly a decade-long major drought alive.
"I thought it might have hit the hole, which would have been...," said McIlroy, trailing off.
"But I'll take a two there. Obviously a great way to finish the round and a bit of a reversal of yesterday, where I made that bogey at the last."
The shot of the day came when Matt Fitzpatrick (28) nailed a hole-in-one at the par-3 15, making him the first U.S. Open defending champion to record an ace in the tournament's 123-year history.
LIV Golf's Johnson made a mess of his second hole and finished with an unsightly quadruple bogey to tumble down the leaderboard, but he battled back to card even par 70 and stay in the hunt going into the weekend.
Course conditions have been favourable for scoring due to a thick marine layer blanketing Los Angeles, but the sun began to shine and wind picked up on Friday afternoon. More sun is forecast over the weekend.
Firmer conditions should make the course located in the heart of Los Angeles a more fitting challenge for the world's best at a major that prides itself as being the greatest test in golf.
The tournament is the first major since the bombshell announcement that the PGA Tour and rival circuit LIV would form a unified commercial entity. The U.S. Justice Department will review the plan to determine if it violates antitrust law, the Wall Street Journal reported on Thursday.
