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What has happened?

In 2016 the French car manufacturer of Peugeot Citroën vehicles, the PSA Group (PSA), were referred to French prosecutors by the consumer watchdog DGCCRF after they seized documents which indicated emissions irregularities in their vehicles.

PSA Group are now under investigation for the possible use of unlawful defeat devices in 1.9 million Euro 5 standard vehicles.

A French government-backed testing programme found that five PSA vehicles emitted significantly more NOx in normal driving conditions when engine temperatures increased. A PSA engineer acknowledged that, by design, the cars’ emissions system is deliberately reduced at higher temperatures to improve fuel efficiency and CO2 emissions outside of cities, where (he argues) NOx emissions are less critical.

In addition, independent testing indicates that several PSA vehicles use thermal windows, which reduce the effectiveness of emissions control systems when the ambient air temperature is above or below certain temperatures. A recent CJEU decision has found that such devices will likely constitute an unlawful defeat device. Read more about the judgment here.

The PSA deny any emissions cheating but face up to €5 billion fines if found guilty of equipping cars with illegal software.

Click here to read further about emissions claims.

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The scandal in numbers


Number of Euro 5 diesel vehicles estimated to be affected


Fine PSA Group face if found guilty by French prosecutors of equipping cars with illegal software


Estimated number of Euro 5 and 6 Peugeot and Citroen vehicles on European roads


Times certain Citroën models exceed regulatory NOx level

Citroën photo

Can I join?

According to current investigations into Peugeot Citroen emissions, most Euro 5 diesel vehicles have been implicated, with reference to particular models:

Peugeot 208
Peugeot 3008
Peugeot 508
Peugeot 807
Peugeot 308
Citroën C4 Picasso II
Citroën C3 II 1.4
Citroën C4 II 1.6
Citroën C4 Picasso II (TH)

However, anybody who bought a Euro 5 or Euro 6 diesel Peugeot or Citroën vehicle in England or Wales can apply to join the claim. If you bought or leased an affected vehicle in Scotland or Northern Ireland, you can still complete our questionnaire, but your claim will be handled slightly differently.

The litigation will be free at the point of use. Harcus Parker will act on a no-win, no-fee basis, and will pay any third-party costs which are necessary in order to progress the claims to trial.


NOx contains both Nitrogen Oxide and Nitrogen Dioxide. NOx is emitted when fossil fuels are burnt, but not completely combusted. Diesel engines are not 100% efficient, meaning that their exhaust emissions contain NOx, as well as greenhouse gases such as carbon dioxide and carbon monoxide, and air pollutants such as particulate matter. NOx worsens air quality and has adverse health effects including contributing to respiratory problems and cancer. Diesel cars are one of the main causes of pollution in our air.

These allow cars to turn down their emissions control system outside the emissions testing environment i.e. when the cars are driven in the real world. Not all defeat devices are cheating devices – some are allowed by regulations. However, in many cases they are used by manufacturers to give the appearance that their diesel vehicles pass emissions tests, when in fact they do not.

The term used to describe the emissions scandal which broke when the German car maker, VW, admitted to fitting more than 11 million of their VW cars with unlawful defeat devices leading to the first major emissions class action lawsuit in the United States.

We use this term to cover both owners of cars, and people who leased their cars.

A senior court of England and Wales dealing with high value and high importance non-criminal matters. This court ruled that it will be bound by findings of the KBA (the German motor authority) that defeat devices are present.