[aerohead]

In 2013, GM published an advertorial for the Chevy Malibu aerodynamics, which included the 'automatic' grille-shutters. Good for delta-Cd 0.007.
I'm guessing that, there's a threshold voltage from a temperature sensor which the ECU recognizes as the 'trigger' for the motor actuator to 'open.'
And then another voltage at which the ECU is satisfied, signaling for 'closure.'
An official GM shop manual would have the data.
In a most primitive setting, the shutters might just respond the the same voltage assigned to the electric cooling fan. They should be wired to fail-open.
A local wrecking lot might have a rear-ended Cruze with a complete front clip that you could examine, and or, salvage parts from. Or E-bay, once you know what you need.