Brainteaser - solution.

Most people see this as a logic problem and concentrate on trying to make sense of the three statements, whereas what you need to focus on is - where is the car? 
We know it's in one of the boxes, so -
If it's in box 1, then the statements on boxes 1 and 2 are both true, and as we know only one statement can be true, it can't be in Box 1.
If it's in Box 3, then the statements on both Boxes 2 and 3 are true, so it can't be there.
So it must be in Box 2.  Does this work?  Yes, if that's where it is then the only true statement is the one on Box 3.
As is always the case - easy when you know how.