I am struggling with understanding of this structure. So here is something I would need to explain:
It has to do something with the car. [It is related to the car somehow.]
But what if I want to say that (hypothetically) "it" (e.g. a monster) must perform an action with/on the car, wouldn't it look the same?
It has to do something with the car. [It must perform an action with the car.]
Or:
He has to do something with the fraud. [He is involved in the fraud.]
He has to do something with his friend. [I want to express that he must do something together with his friend.]
Best Answer
You have put the words the wrong way around in your first example:
This means it involves the car in some way. For example
This means that the pain in my back is somehow related to how I sit.
Has something to do with is an idiom that means is related to or involves. The word something must come before the verb to do for it to mean this.
The other way around means, as you say, that it (whatever it is) must do something with the car. For example:
This means that the junk in my flat needs something doing to it by me.
As an aside, two related idioms are
e.g. "Having hair on my chest has nothing to do with eating the crust of my sandwiches".
In fact there are many possible phrases of the form has X to do with ... . X can be, I think, any adverb that implies quantity. E.g.
The adverb used changes how related it is to, e.g. the car.