Software used by Volkswagen to change pollutant emissions according to temperature and altitude is illegal unless it prevents potentially dangerous sudden engine damage, EU High Court counsel said on Thursday.
The finding, if upheld by the Court of Justice of the European Union (CJEU), would be the latest blow to Volkswagen in a series of post-2015 cases involving the use of illegal software to cheat on emissions tests in the US.
CJEU judges usually follow the opinion of the solicitor general, but are not obliged to do so.
The case brought by consumers in Austria concerns software controlling a valve that recirculates exhaust gases from the engine exhaust port. This reduces emissions of nitrogen oxides (NOx), which can cause respiratory problems in humans.
Software disables the valve at temperatures outside the 15-33 Celsius (59-91 F) range and at altitudes above 1,000 metres (3,280 ft), increasing NOx emissions. Consumers argue that it is a prohibited defeat device for which they should receive compensation.
In his legal opinion, CJEU general counsel Athanasios Rantos said a court ruled last December that the emission control software was illegal, even if it had contributed to preventing engine ageing or clogging.
Rantos said the temperature window was not representative of actual driving conditions in Austria and neighbouring Germany, as the average temperature was well below 15 C. Vehicles were also often driven at altitudes above 1,000 metres.
The software was a ‘defeat device’, he said, and could only be justified if the valve malfunction had a sudden effect on the engine, such as a power failure while driving, even if the vehicle was subject to regular maintenance.
VW said the temperature windows used in VW group vehicles are acceptable because their purpose is to prevent sudden and immediate risks of engine damage.