After last month's announcement of a plan that could pull hundreds of thousands of illegally polluting VW Group diesel cars off the road, one out of every six TDI owners is still in limbo.

That's because the plan covers only the 482,000 cars equipped with Volkswagen's 2.0-liter 4-cylinder turbodiesel engine.

The future remains hazy for nearly 100,000 cars and SUVs equipped with VW Group's 3.0-liter V-6 diesel.

CHECK OUT: VW diesel agreement: what we know (and don't know) in 5 questions

For many owners of the larger cars and SUVs, the massive scandal has been "similar, but different" in terms of scope and Volkswagen's own admissions.

When the EPA announced that Volkswagen's 3-liter V-6 diesel vehicles violated the Clean Air Act in November 2015, the agency noted that those cars and SUVs polluted up to nine times the legal limit in some circumstances—not up to 35 times like the 2-liter vehicles.

The environmental agency was noticeably more stern in its call and letter to the automaker, specifically citing the precise timing of the automaker's "defeat device" software on the V-6 engines as well.

2013 Porsche Cayenne Diesel

2013 Porsche Cayenne Diesel

The EPA said in its statement and in a call announcing the violation that the automaker had timed the EPA's test to the second—1,370 seconds—for a "temperature conditioning" mode that helped the cars illegally pass emissions.

According to the EPA's statement:

At exactly one second after the completion of the initial phases of the standard test procedure, the vehicle immediately changes a number of operating parameters that increase NOx emissions and indicates in the software that it is transitioning to 'normal mode,' where emissions of NOx increase up to nine times the EPA standard, depending on the vehicle and type of driving conditions.

In a statement following the notice from the EPA, Volkswagen of America said it would comply with investigators.

Then, in a bizarre move just hours later, Volkswagen in Germany said it was unaware of any illegal cheat device in the 3-liter's engine management software.

Volkswagen plant

Volkswagen plant

VW officials finally capitulated shortly thereafter.

Owners of 3-liter diesel cars and SUVs weren't initially eligible for the automaker's Goodwill Program, which offered gift cards and extended coverage to owners of 2-liter cars.

And the high-level announcement last month of a massive buyback doesn't include those 3-liter cars—at least not yet.

Earlier this year, computer scientists in Europe unpacked a Volkswagen Sharan's engine control unit that detailed a sophisticated operating procedure that closely mimicked the European emissions test.

Although the automaker hasn't specifically identified how its 2-liter engines skirted federal rules in the U.S., the programmers' detailed explanation wasn't a large logical leap from timing the emissions test.

2014 Volkswagen Touareg TDI

2014 Volkswagen Touareg TDI

Volkswagen will appear June 21 in a federal court in California to detail the final proposed plan for buying back or modifying nearly 500,000 cars.

It's unclear when the automaker will announce what could happen to vehicles equipped with its 3-liter diesel engines. They include the VW Touareg TDI, the Porsche Cayenne Diesel, and the Audi A6, A7, and A8 TDI sedans and Audi Q5 and Q7 TDI utility vehicles.

But the EPA will likely be as strict with the company over those vehicles as it has been with the 4-cylinder cars.

“VW has once again failed its obligation to comply with the law that protects clean air for all Americans,” Cynthia Giles, Assistant Administrator for the Office for EPA’s Enforcement and Compliance Assurance, said in the Nov. 2 statement.

“All companies should be playing by the same rules."


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