Volkswagen Group's use of technology that helped it bypass diesel-engine pollution tests breached European Union rules, the bloc’s top court said.
The use of a so-called defeat device can’t be justified by the fact that “it contributes to preventing the aging or clogging up of the engine,” the EU Court of Justice ruled Thursday. Decisions by the Luxembourg-based EU judges are binding.
Such software “must allow the engine to be protected against sudden and exceptional damage” and “only those immediate risks of damage which give rise to a specific hazard when the vehicle is driven” could justify its use, the court said.
The court was asked to rule in a French prosecution against VW for allegedly deceiving purchasers of diesel vehicles.
VW is facing a wave of investor lawsuits, in addition to claims by drivers for their money back for the loss in value of their diesel cars because of the manipulation exposed by U.S. regulator in September 2015. The scandal has cost VW more than 30 billion euros ($36.7 billion.)
A UK court, in one of the biggest class-action suits filed in that country, ruled in April that VW used a defeat device. The decision allows 91,000 customers to proceed with a class action against the automaker.
In a separate case EU judges ruled in July that VW owners affected by the scandal can sue the automaker over diesel-emission manipulation anywhere in the 27-nation bloc, opening up the possibility of claims anywhere where a car owner lives.
The French case concerned an exhaust gas recirculation (ERG) valve, which can redirect some exhaust gases back into the air supply for the engine to reduce final NOx emissions.
The ERG was adjusted in tests using a device to allow emissions to remain below the regulatory ceiling, but according to an expert's report the device would in normal conditions lead to the partial deactivation of the ERG and higher NOx emissions.
Operation of the ERG would have made maintenance more frequent and expensive because, for example, the engine would clog up more quickly.
VW announced recalls of almost 950,000 vehicles in France following the diesel scandal.
VW said that the court's opinion on the classification of the ERG had no consequences on legal proceedings regarding its diesel cars, in Germany or elsewhere.
"In the legal disputes still ongoing outside of Germany, the outcome ultimately depends on the question of possible damage to the vehicle keepers concerned," it said in a statement.
Reuters contributed to this report
