On Tuesday, the California Air Resources Board (CARB) rejected Volkswagen Group’s proposed fixes for 2.0L diesel engines that were caught with software to cheat the cars’ emissions control systems.

CARB’s decision (PDF) only applies to 75,688 California cars, but this afternoon the US Environmental Protection Agency (EPA), which is also demanding that Volkswagen put forth proposals to fix the diesel vehicles caught with so-called defeat devices, agreed with CARB's decision. In a statement, the EPA said that to-date, the Germany automaker "has not submitted an approvable recall plan to bring the vehicles into compliance and reduce pollution.”

Volkswagen has been scrambling to avoid regulatory blowback, lawsuits, and consumer outrage since the EPA issued a notice of violation (NOV) in September, accusing the automaker of installing defeat devices on diesel vehicles made after 2009. Volkswagen was eventually forced to admit that some 11 million vehicles worldwide could have the defeat device software on them. The software increases emissions by up to 40 times the limit allowed by US regulators when the car is being driven under normal conditions.

Earlier this month, the United States Department of Justice filed a lawsuit against Volkswagen on behalf of the EPA asking for billions in fines. Just last week, a German paper reported that Volkswagen is considering buying more than 115,000 affected vehicles back from consumers in the US because recalling and fixing the cars would be too costly.

In its notice rejecting Volkswagen’s recall plans for 2.0L engines, CARB said that “VW’s submissions are incomplete, substantially deficient, and fall far short of meeting the legal requirements to return these vehicles to the claimed certified configuration.” The Air Resources Board lists a number of reasons why Volkswagen’s proposal was rejected, but it specified that among the most important reasons for the rejection was the fact that “the proposed plans do not sufficiently address impacts on the engine, the vehicle’s overall operation, and all related emissions control technologies, including the OBD [On Board Diagnostics] system.” In other words, Volkswagen failed to specify whether the fix to reduce nitrogen oxide (NO x ) emissions would impact the car’s gas mileage or its projected lifespan.

Recall plans for diesel vehicles with 3.0L engines were not included in the discussion because Volkswagen has until February to submit its proposals for those cars.

Volkswagen had an easier time of getting its recall plan implemented in Europe, where the diesel cars with defeat devices will be given a software update that the company says will take “under half an hour." 1.6L engine vehicles will also be fitted with a “flow rectifier” that mechanics will fit in front of the air mass sensor.

But regulations on vehicle emissions are more stringent in the US, specifically in California. CARB did not detail what exactly Volkswagen had proposed to do to make its affected vehicles compliant with emissions standards. Ars contacted CARB for comment and will update this story if we receive a response.

It seems that Volkswagen Group knew its recall plans for diesel Audis, Jettas, Golfs, Passats, and Beetles wouldn’t fly with state regulators. CARB's statement today noted that Volkswagen Group submitted its recall plans to CARB on December 15 and at the same time requested an extension of unspecified length to submit “complete recall plans.” Today, CARB denied that request (PDF), saying that California regulations “require expeditious action” during a recall.

CARB’s decision comes just a day before Volkswagen CEO Matthias Müller will appear before federal regulators at the EPA to present a fix for cars with defeat devices on them. On Sunday night at the Detroit Auto Show, Müller told NPR that Volkswagen “didn’t lie” to investigators when it submitted vehicle documentation to US regulators without disclosing the defeat devices on the cars. “It was a technical problem,” Müller said to NPR on Sunday night. "We made a default, we had a ... not the right interpretation of the American law. And we had some targets for our technical engineers, and they solved this problem and reached targets with some software solutions which haven't been compatible to the American law.”

Müller later contacted NPR to rephrase his statement. “First of all we fully accept the violation,” he said. "There is no doubt about it. Second, we have to apologize on behalf of Volkswagen for that situation we have created in front of customers, in front of dealers and, of course, to the authorities.”

In a statement made to Ars today, a Volkswagen spokesperson said, "Today's announcement addresses the initial recall plans Volkswagen submitted to CARB in December. Since then, Volkswagen has had constructive discussions with CARB, including last week when we discussed a framework to remediate the TDI emissions issue.This week, we have been working with [US mediator] Kenneth Feinberg to develop a swift, fair and independent program, which will provide a comprehensive remedy for our customers. We are committed to working cooperatively with CARB and other regulators, and we plan to continue our discussions tomorrow when we meet with the EPA."