"The pressure was off of me," Ethier said. "Kemp was the one that came up with the big hit to get us even. We had new life, a fresh start. I was able to get ahead and figured why not give it a shot ahead 2-0. I figured why not. Let's take a chance."
The Dodgers took two of three from Arizona to pull even with the Diamondbacks in the NL West.
"That was a huge win," said Dodgers manager Joe Torre. "It was nice to be able to steal that one."
Brandon Webb and the Diamondbacks had staked Lyon to a three-run lead, but the Diamondbacks closer, pitching in his third straight game, couldn't hold it.
Nomar Garciaparra doubled and James Loney singled. Andruw Jones hit what could have been a double-play grounder to Stephen Drew, but the shortstop bobbled the ball and had to throw to first for the out as Garciaparra scored.
"If we turn that it's potentially a different outcome," said Arizona manager Bob Melvin. "You never know where the game goes after that."
Lyon retired Blake DeWitt on a grounder to short for the second out. But Andy LaRoche singled to right, scoring Loney to make it 4-3, and Kemp doubled to center to score pinch runner Pablo Ozuna and tie the game.
"I fouled off some good pitches until I got a good pitch to hit," Kemp said. "He threw a straight fastball inside and I turned on it."
Ethier followed with a triple high off the center-field wall, scoring Kemp to give the Dodgers their first lead. Russell Martin singled to center for a two-run Dodgers lead.
Lyon (2-4) lasted just two-thirds of an inning, allowing a career-worst five runs and five hits for his fifth blown save. On Saturday, he allowed two runs and three hits in an inning, but got the save.
"My arm felt great today," Lyon said. "It was just a matter of not making pitches when I needed to. The last couple of outings I didn't do a very good job out there. I just need to do a better job of making pitches."
Ramon Troncoso (1-1) was the beneficiary of the rally, striking out five over two innings for his first major league victory. Jonathan Broxton pitched the ninth and surrendered a two-out RBI single to Drew before recording his second straight save.
Webb, trying for his major league-leading 14th win, was effective if not overpowering, allowing six hits with three walks and four strikeouts in eight innings.
"I felt I was falling behind a lot in the count," Webb said. "But I worked out of some jams, made some pitches when I had to and came out pretty much unscathed. It gets frustrating to go out there and not be able to put it where you want it."
Orlando Hudson fueled the Diamondbacks' three-run first inning off with his baserunning.
Drew and Conor Jackson led off the game with consecutive singles and Hudson walked to load the bases. Tony Clark then hit routine grounder to Kent just in front of Hudson, who evaded Kent's initial tag attempt and started running back to first while Drew scored from third. Kent threw to Loney at first to retire Clark and, with Hudson caught in a rundown, Loney threw back to Garciaparra.
Garciaparra glanced briefly at Jackson, who had advanced to third, as he chased Hudson back to the bag. But Hudson dove back to the first-base bag ahead of the tag from a sliding Garciaparra to give the Diamondbacks runners on first and third.
"We gave them a run by messing up the rundown play but we were able to overcome that," Torre said.
Arizona added a run in the sixth when Reynolds led off with a triple and scored on Snyder's suicide squeeze bunt.
Lowe went 5 1/3 innings, allowing four runs and seven hits.
"Sometimes you just have to invent stuff," Lowe said. "This was one of those days."
Los Angeles is 2-45 when trailing after eight innings. ... Snyder was activated from the 15-day disabled list before the game. Snyder missed 14 games with a left testicular fracture and played in one minor league game on a rehab assignment. ... Arizona optioned catcher-infielder Robby Hammock to Triple-A Tucson to make room for Snyder. ... Ozuna had been signed before the game. The 34-year-old hit .281 in 32 games for the Chicago White Sox before he was designated for assignment July 8. To make room for Ozuna, the Dodgers designated infielder Luis Maza for assignment. ... With his home run Saturday, Kent has at least 10 home runs in 17 straight seasons, the longest such streak among active players.