CARB says VW has been "unable to demonstrate the required compliance" for other vehicles affected by the scandal.

US regulators have approved a proposed emissions fix for another batch of Volkswagen vehicles affected by the diesel 'defeat device' scandal.The latest modification approval only applies to the 'Gen 2' 2.0-liter diesel engine used for the 2012-2014 model years, and only for vehicles equipped with automatic transmissions.

Regulators appear to be reviewing the proposals separately for manual-transmission cars, which have not yet received approval to be repaired and brought back into compliance.

"VW has been unable to demonstrate the required compliance, and is reevaluating its proposed emissions modification for these cars," CARB said in a statement.

The decision for Gen 2 cars follows the January approval for Gen 3 engines. Regulators are still reviewing proposed refits for Gen 1 vehicles and others powered by 3.0-liter diesel engines.

"We are advancing on the technical fixes per the settlement agreement as expeditiously as possible. So today's approval is not the end of the story," says CARB executive officer Richard Corey. "VW must still successfully modify thousands of earlier model vehicles, or prepare to buy them back. "