Just as Germany’s car industry seemed to be turning a corner after the diesel emissions scandal, along comes another potentially credibility-shredding story.Volkswagen AG (and its Porsche and Audi subsidiaries), BMW AG and Daimler AG may have colluded for decades to agree on technical standards, thereby impeding competition, Der Spiegel reported on Friday. While the scope of any wrongdoing or potential fines are very unclear, these cartel allegations may yet impose a heavy financial and political price on the carmakers.It’s not as if investors have been queuing up to buy shares in the German car giants anyway, amid fears that the rise of autonomous and electric vehicles will leave them without much of a business model. In Europe, meanwhile, they are having to fight against the efforts of cities to ban many diesel vehicles. New questions about their integrity won’t help. That’s especially true ahead of a German federal election in September. Opposition politicians have every incentive to fling mud at chancellor Angela Merkel’s government, which is perceived as too chummy with the powerful car industry.