Answer:
This is likely the response you're looking for:
The car was not damaged even though it backed into the wall.
.... but, this is also a possibility:
The wall was not damaged even though the car backed into it.
Explanation:
As written, the sentence is ambiguous because of the pronoun 'it' which can refer to both the car and the wall in the same clause. Consequently, the reader doesn't know if the wall was damaged or if the car was damaged.
