If a item is sold to be used…
If a item is sold to be used "for a particular purpose" it has to be able to perform for that particular purpose. In this instance, the purpose was to be driven.
There is a time limit, but this is a usable legal precedent
I was able to get a used car dealer to fix a vehicle that stopped being able to be driven, after showing the court that due to a defect, it could perform as expected at time of perchase