Malukas has been unable to drive competitively since sustaining a wrist injury in a mountain biking accident on 12 February.
He was replaced by Ilott at the subsequent tests and in the season-opening Grand Prix of St. Petersburg, where the 25-year-old Briton finished 13th.
As Malukas continues his recovery, Ilott will again drive one of Arrow McLaren's Chevrolet-powered entries in the upcoming Barber test, as well as in the non-championship $1 Million Challenge.
The event is taking place on 24 March at private motorsport facility The Thermal Club, located in southern California, fewer than 150 miles away from Los Angeles.
The 17-turn, 3.067-mile track will host an open test and qualifying on 23 March before the race on Sunday. While points are not on offer, the winner will take a coveted one-million-dollar prize.
A former European F3, GP3 and Formula 2 frontrunner who made his IndyCar debut in 2021 with Juncos Hollinger Racing, Ilott lost his drive with the Argentine-American squad to Romain Grosjean at the end of last year having managed two top-five finishes as his best results.
"I was expecting to stay in IndyCar, that was the original plan, and circumstances changed as they sometimes do in life," he told Autosport earlier this year.
Source: Autosport