Major car firms found not to have installed emissions-cheating devices

Breaking news from the markets: Major car firms found not to have installed emissions-cheating devicesImage source, Getty ImagesByMarc AshdownBusiness correspondentPublished10 July 2026Vehicles from a host of major car manufacturers did not contain devices alleged to have allowed them to cheat on emissions tests, a judge at the High Court has ruled. More than a dozen manufacturers are being sued by around 1. 6 million motorists over claims that several diesel vehicles made from 2009 onwards contained "prohibited defeat devices" (PDDs).

The cases involved 20 "sample vehicles" made by five manufacturers: Mercedes-Benz, Renault, Nissan, Ford, and Peugeot and Citroen. The 880,000 motorists claimed they had been misled about emissions tests. The ten-week trial concluded in March and, in a 369-page ruling handed down today, Lady Justice Cockerill said most of the strategies did not constitute PDDs, with the exception of one in Mercedes cars that was removed in 2015, and another used in some Peugeot-Citroen vehicles.

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The judgement said: "The Court rejected most of the principal allegations advanced against the manufacturers whose vehicles were examined at trial. "It added: "In the majority of instances, the Court found that the relevant strategy did not constitute a prohibited defeat device. "Mercedes welcomed the ruling but said it disagreed with the court judgement that one of its four sample vehicles was not compliant prior to the software update.

The German carmaker said: "In our view, the emission control software functionalities are justifiable on both technical and legal grounds. We are actively considering all of our available options, including a potential appeal. "Peugeot-Citroën has yet to comment.

Those taking legal action either bought, leased or otherwise acquired a diesel vehicle made by one of the companies, with most living in England and Wales. Barristers for the motorists told the trial the devices installed in the cars allowed the vehicles to detect when they were being tested and alter the amount of harmful emissions produced so they fell within emissions regulations. However, the court found that not every calibration or emissions-control strategy amounted to a defeat device.

"For a defeat device to be found, there needs to be an intention to cause the emissions control system to operate differently when it senses it is being tested," the judge found. "It was not enough for the Claimants simply to establish that the challenged strategies reduced the effectiveness of emissions-control systems outside the relevant testing conditions. "Solicitors for the claimants did note that Justice Cockerill said "if an alternative approach to the meaning of 'defeat device' were taken, a larger number of devices would be established, including devices in each of the lead manufacturers cars".

Financial markets are tracking the development closely as investors assess the likely impact.