What's the Fix for Volkswagen's 'Defeat Device'? Experts Unsure

Facing what has become the worst crisis in its history, Volkswagen is vowing to come up with a fix for its diesel pollution problem "as soon as possible." But how will the German automaker solve the problem of the so-called "defeat device" without compromising performance of the 482,000 VW diesels sold in the U.S.?

So far the company's response to the scandal that erupted on Sept. 18 when the U.S. Environmental Protection Agency accused the automaker of cheating on emissions tests has largely focused on apologies and ousting a number of top executives. But it has taken an initial step toward communicating with its customers with the launch by its U.S. subsidiary of a special website where owners can go for information about the problem.

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"You may have noticed that we have stopped advertising our latest TDI models," the new U.S. consumer website says, referring to the maker's decision to also halt sales of 4-cylinder diesel products. We did this as an interim step while we seek the government approvals that will allow us to offer our 2.0L 4-cylinder TDI models for sale (once more)."

The revelation that VW was selling diesel vehicles secretly designed to fool emissions tests while allowing them to produce up to 40 times the maximum allowable pollution in real-world use has triggered investigations in the U.S. as well as overseas, where millions more diesel models were equipped with the suspect software. The number of lawsuits facing VW also has rapidly grown and criminal charges could follow. The situation, if anything, may grow worse with new revelations indicating senior management may have known for years about the cheating.

In light of that rapidly cascading crisis, industry experts interviewed by say it is far from certain how long it will take the automaker's engineers to devise a solution that will deactivate the "defeat device."

But they did provide insights into the source of the problem and the challenges the maker faces coming up with a fix.

By the middle of the last decade, the experts said, it became clear that VW's old, less advanced diesel design would not meet tougher emission standards, especially in the critical California market. As a result, VW engineers set out to reduce emissions even while also improving mileage and performance.

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Initial optimism for the new WA 189 engine steadily diminished - at least internally. Early on, the company hoped to get as much as 60 miles per gallon, then 50 or more. By the time the diesels were ready for market in 2008, that figure had dropped to around 42, depending upon the model.

The problem was that the catalytic system meant to scrub smog-causing nitrogen oxides wasn't working as well as projected. An alternate approach, which would have injected a derivative of urea into the exhaust-cleaning process, was deemed too costly and only adopted across the board for the 2015 model-year.

The experts say that the "defeat device" apparently was introduced about this time to help address the performance issues.

Among the fixes VW engineers are likely to try would be to rewrite the basic engine software. But the experts warn that this approach could result in a loss of performance and reduced fuel economy.

An alternative might require the installation of new pollution control hardware, as well. That would be costly - and it's not even sure that approach would be practical or possible.

Some observers believe that Volkswagen might have to compensate owners for reduced performance and mileage, perhaps even offer a buyback program, as Fiat Chrysler recently announced in connection with defective Ram pickups.

VW insists it will do whatever it takes, the maker's new website declaring, "We are committed to making this right and preventing it from ever happening again. We will bring these TDI vehicles into compliance with the federal and state emissions regulations."

This spare-no-expense approach is one that turnaround strategists say is absolutely critical if the German maker is to ever rebuild its reputation.

VW should know.

Thirty years ago, it challenged consumers who were complaining about alleged safety problems with the Audi brand's big 5000 model. Ultimately, a federal investigation showed the carmaker was correct, but its seemingly arrogant approach so frustrated consumers that they didn't return to the brand. As a result, Audi almost abandoned the U.S. market.

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A worst-case scenario for Volkswagen would be a steady drips of new revelation. And, indeed, new reports published by several German newspapers, including the weekend Frankfurter Allgemeine Sonntagszeitung, indicate the Volkswagen AG supervisory board was warned of the diesel cheating scam by both a key supplier and some of the company's own engineers.

A letter dated 2007 shows that the automotive mega-supplier Bosch pointed to illegal modifications to its control software, the reports said.

And VW's own technicians flagged the issue for the automaker's board in 2011, they said.

If such reports prove accurate they could complicate not only the carmaker's legal problems but also its efforts to rebuild its reputation. VW has long prided itself on taking a leadership position in green automotive technology. It could be a long time before consumers take that claim seriously again.