The German transport ministry has ordered Mercedes-Benz to recall up to 774,000 cars across Europe after tests found that they contain unauthorised software, or a so-called defeat device, that could be used to manipulate diesel exhaust emissions.
In an official statement, the Kraftfahrt-Bundesamt (KBA) said it had ordered Mercedes to immediately recall selected Vito, C-Class and GLC models in Germany.
“The government will order 238,000 Daimler vehicles to be immediately recalled Germany wide because of unauthorised defeat devices,” the KBA said.
Daimler is the parent company of Mercedes.
Among the models said to be affected are the Vito 119 CDI, C220d and GLC 220d.
The KBA has not indicated the age of the cars involved, although officials suggest they include latest-generation models with Euro 6 emissions certification.
News of the recall comes after the German transport minister, Andreas Scheuer, met with Mercedes chairman Dieter Zetsche in Berlin to discuss what has been described as “irregularities in independent test results of various Mercedes-Benz models featuring the German car maker’s turbocharged four-cylinder diesel engine”.
Among the features brought into question by the KBA is software used to regulate the amount of Ad Blue solution injected into the SCR filter on the models in question.
Following the discussion, Scheuer said Daimler had pledged to remove the suspect software and co-operate with authorities.
Autocar understands that the software is programmed to lower the amount of Ad Blue being injected after a prescribed time. This lowers the efficiency of the SCR filter and leads to much higher nitrous oxide emissions in real-world driving conditions than those claimed by Mercedes under test conditions.
A report in German newspaper Bild am Sonntag suggests the German Transport Ministry has identified up to five illegal Ad Blue and/or SCR switch off functions in various Mercedes-Benz diesel models.
In accepting the recall, Zetsche said Mercedes-Benz had developed a technical solution that would enable it to update the software in a move he suggests would see the company avoid possible fines by the European Union. However, in a separate statement, Daimler said the question over the legality of the software still needed to be clarified.
EU Commissioner Elzbieta Bienkowska tweeted her recommendation that all EU member states follow Germany's example of calling a recall: "We need mandatory recalls in all 28EU Member States. Other countries should follow quickly." She also urged a step-up in the progress of EVs.
In recent weeks, Mercedes has defended its diesel engine software, saying it conforms to the law prescribed by the EU. In certain situations, car makers are permitted to switch off the SCR filter in diesel engines in the interests of engine longevity.
At this stage, it is not known how many cars are affected by the recall in the UK. However, given the popularity of models such as the C220d and GLC 220d, the number is thought to be significant.
An official from the KBA told Autocar UK that it is only authorised to order a recall of cars within its own borders or cars issued with a pan-European road-worthiness certification, suggesting Mercedes diesel owners in the UK will have to wait until full details to a possible Britain-wide recall are revealed.