Nissan’s Norman Nato set the pace in the second free practice session of the weekend in Portland.
Nato jumped to the top of the times in the closing stages of the session with a time of 1m09.101s, 0.05s slower than the fastest lap set in FP1.
Maximilian Guenther, who spent most of the session at the top of the order, finished second, 0.139s behind Nato.
As in FP1, a number of drivers ran into traffic issues on their laps as they tried to find the best position on the Portland circuit. Among those was Andre Lotterer, who had to take to the grass to avoid Sergio Sette Camara at the end of the lap. Sette Camara was shown the white and black flag for the incident.
Despite the traffic issues and a few runs over the grass and onto escape roads, it was an incident free session.
Rene Rast set the pace early on with a time of 1m09.255s, just ahead of team-mate Jake Hughes, but dropped down the order as Guenther improved. He would finish fourth quickest, behind Sam Bird. Bird had limited running during the session, but was still able to finish comfortably faster than team-mate Mitch Evans, who only placed P21.
Title contenders Jake Dennis and Nick Cassidy also struggled to find pace in the session, finishing 19th and 20th respectively. Meanwhile, championship leader Pascal Wehrlein took ninth, ahead of team-mate Antonio Felix Da Costa.
Jean-Eric Vergne was the quickest DS Penske driver in P5, finishing ahead of Sacha Fenestraz, Hughes and Edoardo Mortara.