Three weeks before elections, Chancellor Angela Merkel will Monday face the toxic "dieselgate" scandal which pits the interests of Germany's powerful auto sector against public health fears over air pollution.
Merkel will from 0900 GMT meet German town and city leaders who are considering full or partial bans on diesel vehicles to cut down on nitrogen oxides (NOx) emissions that cause smog, acid rain and fine particle pollution.
The chancellor has made clear she will try to stop such bans, fearful of the impact on the industry whose global titans like VW, Audi, Mercedes and BMW earn billions in export euros and employ up to 900,000 people.
"We are working to prevent driving bans," Merkel recently told top-selling Bild daily, adding that this would be "tough work" since both local governments and independent courts can weigh in on the issue.
The emissions cheating scandal that has engulfed VW, its subsidiaries and other companies since 2015 has already depressed the resale value of diesel cars -- a powerful election issue for millions of voters.
While Merkel has often spoken of her long-term vision of a carbon-free economy dominated by green-tech and climate friendly e-mobility, she has made clear that, when it comes to the diesel issue, "this is 2017".
Speaking in a TV interview last week, she labelled diesel and other combustion engines "bridge technologies" toward a cleaner future that "will be needed not just for years but, I would say, for decades more".
VW plunged into its worst ever crisis when US investigators in 2015 forced it to admit having fitted 11 million diesel engines with "defeat devices" to cheat on emissions tests and hide the fact they spewed as much as 30 times the permissible limits of dangerous nitrogen oxides (NOx) during normal driving.
While the company has agreed to pay $4.3 billion in penalties and $17.5 billion in civil settlements in the United States, VW has escaped fines of such magnitude in Europe.
At a recent government-industry "diesel summit" in Germany, carmakers promised to fix the problem with software patches, rather than more expensive hardware fixes, while also offering trade-in incentives.
Environmental group Greenpeace fumed that this was too little too late and showed that Germany had missed the boat on shifting toward modern, clean transport systems.
"Instead of protecting people in cities from toxic exhaust fumes and promoting innovation in the auto industry, the government continues to tolerate these pretend-solutions," charged Greenpeace transport expert Andree Boehling.
The federal office for environmental protection has meanwhile confirmed that the software patches are insufficient to significantly reduce urban air pollution.
Juergen Resch of environmental pressure group DUH, which is behind many of the court challenges, has vowed to bring even more cases, stressing that NOx is linked to over 10,000 premature deaths per year in Germany.
Merkel was dubbed the "car chancellor" in 2013 after she went to bat for the sector and argued against an EU cap on emissions.
But she and her centre-right CDU are not alone in having cosy ties with the auto sector, the backbone of the German economy.
Germany's other major party, the centre-left Social Democrats (SPD), also have deep ties. The SPD stronghold state of Lower Saxony, where VW is based, has a 20-percent stake in the company.
Merkel has repeatedly said she was "angered" by the auto sector's transgressions and demanded more "honesty and transparency" in future.
However, she has also spoken out against costly hardware fixes for diesel engines, refused to commit to a date by when Germany should phase out fossil fuel-powered cars, as Britain and France have vowed to do by 2040, or to commit to a plan for binding quotas on electric cars.
At the air quality "summit" on Monday, Merkel has said she will suggest a compromise solution where the most polluted municipalities could get funding to speed up the development of e-car charging stations and better public transport.
"To turn these worst-affected cities into pioneers in modern mobility, that would be one of the ideas," she said last week.