Turrets can be turned to face without it counting as movement.
Vehicles can pivot on the spot as discussed above and as this is not considered to be movement it does not affect firing. Immobilised vehicles cannot pivot on the spot.
Turning to Face
Source: Core Rulebook 3E, p. 83
Turning a turret to face, or pivoting the vehicle itself, does not count as movement and so does not affect firing — unless the vehicle is immobilised.