The software qualifies under state and federal laws as a so-called auxiliary emissions control device - something that modifies the performance of emissions equipment. Volkswagen and regulators declined to say whether this software was intended to defeat emissions control tests, like the software that the automaker already admitted last month that it had installed in 11 million diesel cars since the 2009 model year. "VW did very recently provide EPA with very preliminary information on an auxiliary emissions control device that VW said was included in one or more model years," said Nick Conger, an agency spokesman. He added that federal and California regulators "are investigating the nature and purpose of this recently identified device." Damage spirals Volkswagen is already struggling with the spiralling cost and growing damage to its image from last month's revelation that it had installed software to detect when a car was undergoing an emissions test and minimise harmful emissions. When not being tested, the cars would emit up to 40 times the allowable levels of pollution. Volkswagen and regulators refrained from characterising the second software program in any way. The automaker gave no indication of whether it was also devised to defeat emissions tests.

"In Volkswagen Group of America's recent discussions with the regulators, we described to the EPA and CARB that our emissions control strategy also included a software feature that should be disclosed to and approved by them," the automaker said. Stanley Young, a spokesman for the California Air Resources Board, said the state agency was investigating the nature of the second device, but declined to provide specifics because Volkswagen's application "is still pending." Young said that while Volkswagen has withdrawn its 2016 application with federal regulators, it has not withdrawn the similar application filed with California regulators. "We're still going through all the information they provided and determining the next step," he said. Another defeat device? Under normal circumstances, automakers are allowed to use the auxiliary emissions control devices under deals negotiated with regulators that provide for higher emissions in very specific circumstances (like going up a steep hill, or in very cold weather). But they must be disclosed.

Young said he could not comment on exactly when Volkswagen disclosed the existence of its auxiliary emissions control device, or AECD. "What we don't know yet is if the 2016 AECD is also a defeat device, or is a device that meets the guidance previously given by EPA," said John German, a senior fellow specialising in emissions and efficiency technology at the International Council on Clean Transportation, the nonprofit group that first noticed that the real-world emissions of Volkswagen diesels in the United States were far above regulatory limits. Federal regulators warned manufacturers of heavy-duty trucks in 1998 that it would strictly scrutinise any devices that interfered with the normal operation of emissions control equipment, after finding that they had installed systems similar to what Volkswagen disclosed last month in its diesel cars. Dan Becker, the director of the Safe Climate Campaign at the Center for Auto Safety, a nonprofit Washington research group, said that Volkswagen's new admission was a potential violation of the law. "They put it in their vehicles, and then they signed a certification petition to the regulator saying what they put in their vehicles and didn't mention it," he said. "It's certainly a material omission."

Lawmakers did not discuss Volkswagen's admission at length during the hearing. But Fred Upton, a Republican representative from Michigan, openly wondered if Volkswagen was skirting regulations in other ways. "If they were willing to cut corners here, what else have they done?" he asked. 'Our plan is to fix the cars' In addition to disclosing the second investigation in his opening testimony, Volkswagen's US boss laid out the automaker's plans to fix the cars currently affected and cautioned the panel that owners might have to wait a year or two. Most of the more than 480,000 affected cars in the United States alone will need a "major fix," Horn said, including a hardware and software change. That repair, which would be applicable to almost 70 per cent of those vehicles, may consume as much as 10 hours of work per car and might not get started until next year. The remaining vehicles are expected to be fixed next year, he said. "This is pretty shocking for people," said one lawmaker,, expressing dismay at the scandal and demanding a specific timeline for fixes. "Asking customers for patience is really just not sufficient."

Some lawmakers asked Horn why Volkswagen did not replace the vehicles -- a costly proposition -- and, although he emphasised repairs, he said Volkswagen might consider an option like a buyback. "Our plan is not to buy back the inventory," Horn said. "Our plan is to fix the cars." Although Horn apologised for the deception and even said he felt deceived by the scandal, he came under withering criticism from lawmakers for not delivering a concrete deadline for fixing most of the cars, and not providing more details about how the scheme was conceived and who was responsible. In response to questioning by Texas Republican Joe Barton, Horn said that neither Volkswagen's supervisory board nor its top executives ordered the emissions deception. Instead, he attributed the decision to "a couple of software engineers who put this in for whatever reason." After an incredulous Barton expressed doubts that top Volkswagen executives in Germany were unaware of the cheating before September, Horn did not argue.

"I agree it is very hard to believe," he said. "This was not a corporate decision," Horn maintained. "This was something individuals did." The New York Times