Larson had taken the lead from Truex, the race’s defending winner, on Lap 22 and led 78 consecutive laps before falling to second on the 100th and last lap of the opening segment.
It’s the series-leading 16th stage victory of the season for Truex, who has 36 playoff points and likely will gain another 15 by clinching the regular-season title in Sunday’s race.
The playoffs continued to take shape as Clint Bowyer, the only driver with a realistic shot of breaking into the field of 16 on points, suffered an engine problem during his first pit stop. Bowyer’s No. 14 Ford will finish last, and its misfortune makes it more likely that Chase Elliott, Matt Kenseth and Jamie McMurray will make the playoffs on points, barring a victory by a winless driver.
After Darlington, the Sept. 9 race at Richmond International Raceway will conclude the regular season.
During the ensuing yellow-flag pit stops, pole-sitter Harvick, who had led the first 18 laps, slid deep in his stall and lost nine spots on a slow stop. His No. 4 Ford quickly sliced through traffic and had moved into second within 50 laps.
Ryan Blaney also fell two laps down early after hitting the wall in the first five laps and then missing the entry to the pits for repairs.