What we know: the Volkswagen emissions test fraud scandal

BERLIN (AP) — Just one week ago Volkswagen was a company oozing confidence, the world's best-selling automaker with a global brand that appealed to car buyers seeking trustworthy German engineering at an affordable price.

[...] the company's fortunes — and its share price — have crashed amid a scandal over rigged emissions tests.

Researchers at West Virginia University, tipped off by an environmental group, conducted tests on several diesel vehicles and discovered that two Volkswagen models, a 2012 VW Jetta and a 2013 VW Passat, had much higher emissions than permitted.

[...] EPA announced Sept. 18 that Volkswagen had skirted clean air rules by cheating on tests of its diesel cars.

Diesel vehicles are more efficient than those powered by regular gas but emit higher levels of nitrogen oxides, or NOx, which can contribute to ozone buildup and respiratory illnesses.

The company faces three big challenges ahead: satisfying regulators that it now meets all the emissions rules, rebuilding customers' trust in its tarnished brand and restoring investor confidence.

According to a report Saturday by German daily Handelsblatt, VW is planning to offer a free fix for the 11 million affected vehicles and customers will be contacted in the coming weeks.