Six years after the housing crisis, investors are snapping up a new crop of subprime bonds backed by auto loans. Ratings companies are awarding the bonds top grades and buyers have almost no way to determine the accuracy of the information those ratings use as criteria. Auto lenders also collect less information on borrowers than in mortgage lending because dealers want buyers to be able to drive off the lot that day. Subprime auto payments more than 60 days late climbed to 3.6 percent of the debt outstanding in July, from 3 percent the year before. But none of that has curbed demand for the bonds; Wall Street sold $17.7 billion of the bonds this year through Sept. 26, a pace that would make 2014 the busiest year since 2006.