PHOENIX — Arizona Attorney General Mark Brnovich filed a consumer fraud lawsuit Tuesday against Volkswagen over the sale of supposed low-polluting diesel vehicles that were anything but that.

Brnovich said potentially 4,000 Arizonans were effectively duped into buying vehicles with a special diesel engine that was advertised as having just a fraction of the emissions of similar cars. Buyers paid anywhere from $1,000 to $7,000 more than for comparable vehicles.

VW engineers programmed the vehicle to know when its emissions were being measured and to go into a low-power operating mode that sharply cut pollutants. Once off the test devices, the engine returned to its normal mode, producing more power — and as much as 40 times the maximum allowable standards of nitrogen oxide pollutants.

VW has effectively admitted that about the vehicles sold from 2008 to 2015.

Company spokeswoman Jeannine Ginivan said Tuesday VW will not comment on specific lawsuits. But she said Volkswagen is working cooperatively with the Environmental Protection Agency and California Air Resources board “to resolve these issues as quickly as possible.”

“We are committed to regaining the trust of our customers and dealers and will continue to cooperate with all relevant government agencies,” she said.

Other states already have filed actions. Brnovich said he decided to go it alone because he thinks he can get more money out of the corporation.

Arizona’s consumer fraud laws have a maximum penalty of $10,000 per violation. That means a potential penalty of $40 million, even before he seeks restitution for the buyers who paid for the benefit of lower-polluting vehicles that they did not get.

Brnovich also pointed out Arizona laws make false advertising a violation. That makes each ad and each commercial run in the state a separate offense, he said.

Some of the lawsuits filed by other states concentrate not on the issue of fraud but on air quality violations. But Brnovich said it remains to be seen whether the vehicles are violating Arizona emission standards.

Filing the lawsuit under consumer fraud laws makes for a much clearer case, he said. “It’s really a claim of restitution based on the diminished value” of the vehicle,” Brnovich said. “More importantly, Arizona consumers were promised their cars would have a certain amount of gas mileage, and they’re not getting that gas mileage.”

Brnovich said more claims may be added as the discovery process begins and the state gets a look at company documents and interviews VW officials and engineers. “We’ll get to the bottom of this, exactly what Volkswagen knew and when they knew it and how they manipulated the data,” he said.

The state has hired outside counsel to pursue the measure, including former federal prosecutor and judge Stephen Larson, and Richard McCune, who Brnovich said has experience in vehicle manufacture fraud and product liability.

A spokeswoman for Brnovich, Mia Garcia, said the attorneys will be paid a share of what the state recovers in penalties. That will not cut into any reimbursement for buyers the state obtains, she said.

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