0728 GMT February 25, 2020
The German makers have decided to recall the vehicles as a voluntary measure following an investigation launched in the wake of the Volkswagen engine-rigging scandal, AFP reported.
A probe has been carried out into the emissions values of all models on the roads in Germany in recent months.
The source said that the companies have been told to make changes to devices which switch off systems to remove harmful nitric oxide from cars' exhaust under specific temperatures.
The systems for cleaning pollutants are switched off at low temperatures to protect motors or prevent a possible accident, as is allowed by EU regulations.
But it was not clear whether some makers used this regulation to bend the rules.
According to the weekly magazine Der Spiegel, the technology stems largely from German car parts maker Bosch.
Neither Volkswagen, whose brands include VW, Audi and Porsche, nor Opel, a subsidiary of US giant General Motors, were immediately available to comment on the information.
Contacted by AFP, a spokesman for Daimler, which owns Mercedes-Benz, declined to comment on what he termed as "speculation."
This new irregularity differs from the engine-rigging scam uncovered at VW last year which triggered a worldwide emissions-cheating scandal.
VW admitted last September to installing so-called "defeat devices" in 11 million diesel engines worldwide.
This sophisticated software deliberately skews emissions readings when vehicles are undergoing tests.