Nowadays many people bulk-import previously designed mesh models from outside the grid from various sources. Often these are sold on Marketplace full permission for builders.
While they can look nice, if they are not specially prepared for actual use as a scripted object by somebody familiar with vehicle building, they will have limited functionality.
In most cases you will want to augment the model with your own root prim, and often overlaying the wheels with simple invisible prim wheels, and leaving the models displayed wheels to spin/turn and remain non-solid.
If prims or prim faces are not set correctly to be scripted for lights, you may have to link your own on. Things like car doors should be individual prims with an inside face, so that they can be scripted to open and close.
You may find it best to replace wheels with ones specially designed for SL use.