Examine the vehicle with E, and look over the diagram tile by tile to find the wheels. If they’re greyed out, they’re completely demolished and have to be replaced. Usually, if a randomly generated car has one broken wheel, they’ll all be broken. You should also have a Wheels indicator on the Examine menu, which will show Enough, Unbalanced or Lack, depending on how many functional wheels the vehicle has versus how many it needs to drive.