Green’s Dictionary of Slang

louie n.2

also lewy
[the initial letter]

in driving, a left turn; usu. in phr. below.

Online Sl. Dict. [Internet] louie n 1. left-hand turn. One either ‘does’ or ‘makes’ a louie. (‘Make a louie at the next light.’).
[US]Hope College ‘Dict. of New Terms’ [Internet] louee n. Similar to a u-turn, yet this term is used when you turn right to go left.
[US]Eble Campus Sl. Nov. 4: lewy – left turn.
[US]P. Beatty Sellout (2016) 50: After the light changed [...] your dad zipped round them and, while making a louie, yelled something.

In phrases

hang a louie (v.) (also hang a louis) [hang v.7 ]

to turn left.

[US]Coshocton Trib. (OH) 15 Mar. 4/4: Dear Helen: I thought you might like to hear one of the slang-things we read in your column has made it big at our school, but in a different way. You said ‘Hang a Roscoe’ or ‘Hang a Louie’ was ‘turn to the right’ or ‘left’ while you’re driving, as in ‘Hang a Roscoe at the clash’ (intersection).
[US]Current Sl. II:4 6: Hang a Louis, v. To turn left.
[US]G. Underwood ‘Razorback Sl.’ in AS L 1/2 55: hang a Louie ‘turn left’.