California rejects VW's plan to fix emissions problem

California's air-quality authority has again rejected Volkswagen Group's plan to recall and repair 16,000 of its polluting vehicles with six-cylinder 3-litre diesel engines in the state, saying the proposal is too vague.

The US Environmental Protection Agency, which has been acting in concert with the California Air Resources Board, issued its own statement on Wednesday saying it also finds VW's plan to be incomplete.

There are believed to be about 85,000 VW vehicles with 3-litre diesel engines in the US from the 2009 to 2016 model years.

The California board's decision complicates VW's situation as it struggles to come up with a cost-effective solution to repair its larger diesel vehicles. The latest case is the next step after the agreement announced last month that will fix or buy back cars with four-cylinder, 2-litre diesel engines and compensate owners.

The rejection affects Volkswagen, Audi and Porsche vehicles -- all part of the VW Group -- with the larger diesel engines.

"VW's and Audi's submissions are incomplete, substantially deficient, and fall far short of meeting the legal requirements to return those vehicles to the claimed certified configuration," says the letter sent Wednesday to VW Group. A similar letter was sent to Porsche.

The board says Audi admitted in November that its 3-litre diesels have previously undisclosed technology installed that act as "defeat devices", circumventing the vehicles' emissions control systems.

The same finding had earlier been made regarding the 2-litre diesel engines. In that case, VW admitted that software had been inserted to turn on emissions controls when the system detected the cars were undergoing pollution testing, and then turn the controls off for everyday driving.

In February, VW submitted a letter that was supposed to outline how the vehicles didn't meet the requirements of the law, but the board says it rejected it as falling short.

This time, VW is found to have not met the standard again. The board's letter says VW and Audi aren't telling them what exactly they did to the cars to make them beat the requirements of the law. Without knowing what they did, the board says it is hard to know whether a remedy is feasible or adequate.

VW's plan doesn't disclose exactly how it plans to fix the cars or contain data to show the fix will work. And the plan also doesn't tell the board how the proposed repairs will act on the car's driveability or durability.

In reaction, VW issued a statement calling the board's rejection "a procedural step" under the law and pledging that VW will "continue to work closely with" the board and EPA to come up with a plan to resolve the issue.

Last month, the board and EPA announced Volkswagen will pay up to $14.7 billion to settle claims over 475,000 cars with 2-litre diesel engines nationally. VW will offer to buy back or repair cars and offer payments up to $10,000 for each vehicle to owners.

The deal was called the largest of its kind ever.

Volkswagen also agreed to pay $2.7 billion in fines and spend $2 billion on clean-emissions technology.