Here are key points about "dieselgate".
- Exposed in 2015 -
===================
On September 18, 2015, the US Environmental Protection Agency (EPA) reported that VW had installed illegal "defeat devices" in hundreds of thousands of engines in the United States since 2009.
The software -- used in the Volkswagen, Porsche, Audi, Seat and Skoda brands -- helped the cars meet exhaust pollution standards when monitored in tests even though their emissions actually exceeded the limits.
It meant that some cars spewed out up to 40 times more harmful nitrogen oxide -- linked to respiratory and cardiovascular diseases -- than legally allowed.
The company later admitted that 11 million diesel vehicles worldwide, including 8.5 million in Europe and 600,000 in the United States, had been fitted with the software, most of them in the VW brand.
- Legal fall-out -
==================
VW chief executive Martin Winterkorn, who stepped down five days after the scandal broke, was in April 2019 charged with serious fraud, unfair competition and breach of trust.
Eight former and current executives and an Audi official have been charged in the United States, including Winterkorn.
Audi chief executive Rupert Stadler was charged in July 2019 with fraud, falsifying certifications and illegal advertising in connection with the "defeat devices".
VW's guilty plea to a US criminal case in March 2017 settled its legal entanglements there, bringing to around $22 billion the amount it agreed to pay in fines and compensation to owners and dealers and for environmental clean-up.
The group still faces investigations and lawsuits around the world, in Europe the countries include Britain, France, Germany, Italy and Poland.
- Costs for VW -
================
The scandal has so far cost VW around 30 billion euros in fines, compensation and buybacks, mainly in the United States.
The company announced a net loss of nearly 1.6 billion euros in 2015, its first in 20 years, after setting aside billions to cover the costs of the dieselgate.
In June 2018 it agreed to pay a one-billion-euro fine in Germany, admitting its responsibility for the diesel crisis.
Audi agreed in October 2018 to pay an 800-million-euro fine and Porsche was in May 2019 ordered to pay a fine of 535 million euros.
- Other carmakers? -
======================
Tests in the wake of the scandal found that diesel engines by other carmakers were also more polluting on the road than during testing.
But none have so far admitted to mass cheating.
However Mercedes-Benz maker Daimler was in June 2018 ordered to recall 774,000 diesel vehicles across Europe because they too were fitted with illegal "defeat devices".
Fiat Chrysler agreed in January 2019 to a pay $515 million to settle claims it installed the software.
And in February 2019 German prosecutors fined high-end carmaker BMW 8.5 million euros over diesel cars with higher harmful emissions than allowed, though they found no criminal wrong-doing.
Opel is also being investigated.
- Market reaction -
=====================
A study released in March 2017 said that pollution from 2.6 million rigged VW cars sold in Germany would likely cause 1,200 premature deaths in Europe because of the excess emissions.
In Germany more than 410,000 customers are demanding compensation, as are investors.
More generally, European drivers appear to have largely shrugged off the controversy while VW sales have fallen in the United States.
VW said in July 2019 it expects "slightly higher" unit sales for the year than in 2018.