Car locks do not use a pin tumbler system. When it comes to vehicles, in general, they will most likely use wafer locks or sliders. To tell what your car has simply look at the key. If there is biting (serrations that break from the smoothness of the key blade) on both sides then your lock uses wafers. If you have a very rectangular key with a kind of snake pattern engraved in it (usually on two sides) then your lock uses sliders. In either case, they are different from a pin tumbler lick.
Wafer Locks– This type of lock is bay far the closest to a pin tumbler lock. How it varies is that one wafer that is moved, instead of a stack of pins. These wafers must be elevated and depressed to a certain height. If they are not moved to the correct specifications then the wafers will bind at the shear line, keeping the plug from rotating.
Slider Locks– The snake like path on the side of you key is going to move sliders within the lock. They act very similarly to wafers, and, a a result, are the natural evolution for the automotive industry. How they work is the path on the key will move the sliders either up or down, to a very specific place. Once all the sliders are aligned, this will allow the plug to rotate.
What would happen if you tried a bump key on a car?
If anything happens, it is going to be your lock and/ or key breaking. When you strike the bump key with your hammer, the top wafers (assuming the car has wafers) will jump. There will still be bottom wafers that remain unmoved. If the lock has sliders, then jolting the lock would do even less. An impractical amount of knowledge about the specific vehicle lock would be needed just to make an attempt at a functioning wafer lock bump key. If you were to try and move all the wafers simultaneously then you need to know which are being moved up and which are being moved down. For sliders this is not even an idea worth contemplating. There is no set point in the lock where you can move the sliders uniformly and open the device.
Why it Really Doesn’t Matter
From a security standpoint, none of this should be that alarming. Cars and other vehicles are ultimately insecure. With motorcycles, there are much more affordable bypasses for ignitions and locks. With cars, most can be opened with a chunk of wood and a stick. If a criminal is going to try and steal a car, and they are going to pit some effort into learning a new skill, it would make sense to learn other avenues. The bump type methods of opening require too much trial and error for most people. Just because the lock can not be bumped does not mean it can not be opened a different way.