[1] In the Pro Lite Trucks, he won 2014 Rookie of the Year honors with a best finish of second at Lake Elsinore Motorsports Park.

[10] In 2018, he scored his first SST win in the Grand Prix of Long Beach after taking the lead before the race was called for Apdaly Lopez's wreck.

[11] He recorded four more wins at Detroit,[12] Texas Motor Speedway,[13] Sydney Motorsport Park,[14] and Glen Helen Raceway[15] as he finished second in the championship to Matthew Brabham by 50 points.

[16] In June 2019, Harlien made his stock car racing debut in the ARCA Menards Series at World Wide Technology Raceway at Gateway, driving the No.

[17][18] After not racing in 2020 and 2021 to focus on his schooling, Harlien rejoined SST for the 2022 season opener at Long Beach.

[20][21] Harlien scored another win at Bristol Motor Speedway and claimed the championship by 25 points on runner-up Max Gordon.