Volkswagen is making slow progress on fixing cars equipped with illicit engine software in Europe, having repaired less than 10 percent of the 8.5 million affected models, the company said on Monday.

Germany’s KBA motor vehicle authority has approved proposed fixes that would resolve the problem in about 5.1 million vehicles, said the VW manager in charge of the European diesel recall necessitated by the emissions cheating scandal that has engulfed the company.

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“Ten percent of this (number) have been retrofitted with good results,” Manfred Bort said in VW’s in-house journal “inside” published on Monday.

Of the roughly 11 million vehicles affected globally, about 8.5 million are in Europe.

VW group models with 1.2 liter and 2.0 liter engines require only a software update on pollution control systems, but about 3 million 1.6 liter models also require a mesh to be installed near the air filter.

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Volkswagen vlkay , Europe’s largest automaker, is in the midst of developing and testing software variants to fix all the cars and will do “everything” to secure the KBA’s approval of its solutions by November, Bort said.

The German manufacturer has said the majority of the 8.5 million cars in Europe can be repaired this year, but an unspecified number will have to wait until 2017.

“We want to inform all affected customers in Germany by the end of the year that the technical solution is available,” Bort said.