Kirkwood left it until the final two minutes of the session to take the top spot, with a 1m06.2878s clinching him his first series pole.
Having topped his group in the first part of qualifying, Kirkwood finished third in Q2 behind championship leader Pato O’Ward and Romain Grosjean, with his quickest time 0.13s off the lead despite having briefly topped the session.
But he bounced back in the Fast Six, taking pole ahead of former Formula 1 drivers Ericsson, who secured his best street/road course qualifying result for Chip Ganassi Racing, and Andretti team-mate Grosjean.
Kirkwood’s previous best qualifying result had been fifth at the season-opener in St Petersburg.
Arrow McLaren driver Ward initially led the Fast Six from Grosjean, despite the Frenchman having suffered a broken left-rear toelink in Q2.
Alex Palou then moved his Chip Ganassi Racing car to the top before being displaced by Grosjean, but the St. Pete polesitter’s 1m06.5347s wasn’t enough as he lost time at the hairpin.
With fresh tyres at his disposal, Kirkwood then went third, before securing the top spot.
Marcus Ericsson, Chip Ganassi Racing Honda
Photo by: Jake Galstad / Motorsport Images
Ericsson was only 0.0375s behind, ahead of Grosjean and shading team-mates Palou and Scott Dixon, who line up fourth and fifth.
O’Ward locked up under braking for Turn 9 to settle for sixth, despite having been a pre-qualifying favourite.
Grosjean led Q2, rocketing to the top of the times with a 1m06.3246s, ahead of O’Ward and Kirkwood.
Then, on fresh alternates O’Ward jumped to the top of the times, just before Marcus Armstrong brought out a red flag by sliding under hard braking into the tyre wall at Turn 9 with barely a minute to go.
Heading back out, Kirkwood opted for used tyres, to save a set of greens for the Firestone Fast Six, while his rivals who didn’t have the luxury of already being in the top six times had to grab a fresh set and try and bump their way in.
Grosjean got it all right to jump to the top, leading from O’Ward, Kirkwood, Ericsson, Palou and Dixon.
Kirkwood led Group 1 in Q1 as David Malukas damaged a rear wheel on his Dale Coyne Racing car at Turn 8 on his second lap before colliding with the Turn 3 wall the following lap, prompting a red flag.
Palou led Group 2 from Dixon and O’Ward.