Nissan e.dams' Oliver Rowland was quickest in the second free practice session in New York on Saturday morning.
The British driver set a time of 1:09.965, which was just about enough to give him top spot ahead of Antonio Felix da Costa (BMW i Andretti Motorsport) who was just 0.083 behind.
Rounding out the top five were Rowland's team-mate Sebastien Buemi, da Costa's team-mate Alexander Sims, and Envision Virgin Racing's Robin Frijns.
It was warm on track again, with a temperature of 36 degrees being recorded despite it being just 10am local time.
A lot of different drivers took their turn at the top of the timesheets as the session went on, with the likes of Jean-Eric Vergne, Lucas di Grassi, Jerome d'Ambrosio and Antonio Felix da Costa all taking the P1 spot at some point.
In the end it was Rowland who managed to put in the quickest time of the session, and he will go into qualifying confident of claiming his fourth pole position of the season.
For the top two in the championship, it wasn't a session to write home about; points leader Vergne was 17th overall after locking up and using the run-off for the third time already this weekend. His main title rival di Grassi didn't do much better, finishing the session 16th.
Qualifying takes place at 11:45 local time, with three crucial championship points on offer for whoever can secure pole position.