Volkswagen's emissions-test cheating scandal spilled over to the wider car industry on Friday as Germany's top manufacturers agreed to recall 630,000 vehicles to tweak diesel engine software technology blamed for causing high pollution.
As part of a widening clampdown on health-threatening nitrogen oxide (NOx) emissions, Porsche, Volkswagen, Opel, Audi and Mercedes diesel cars will be recalled to fix engine management systems, a German government official said.
BMW, which invested in fuel saving technologies earlier than most rivals, was not part of the recall, the official said.
Engine management systems and software have come under scrutiny ever since Volkswagen (VW) in September admitted it had installed programmes which cheat diesel emissions tests.
Late on Thursday, VW agreed a framework settlement with the US Justice Department, state of California, the US Environmental Protection Agency and Federal Trade Commission, as well as lawyers for car owners who filed class action civil lawsuits.
Though no other carmaker has been found to use so-called "defeat devices", regulators and environmental groups have criticised the widespread use of engine management systems which switch off emissions treatment in order to improve engine performance and increase the interval between services.
European tests have found several carmakers using a legal loophole allowing them to throttle back emissions treatments under certain circumstances, ostensibly to protect engines.
Following extensive testing, the German motor transport authority KBA questioned whether the use of this loophole was always justified and necessary, the German official said.