A US investigation into illegal ‘defeat’ software installed in certain Mercedes-Benz diesel cars has revealed numerous bypass functions temporarily used before before going into a “dirty mode”, according to a report published by German newspaper Bild am Sonntag.
The outlet cites information obtained from a report by the US Department of Justice into various software programs developed by the German maker’s engineers that allowed unspecified diesel models to pass US emission tests through the manipulation of the engine and its selective catalytic reduction filter.
Vehicles are subject to various US emissions tests and it is alleged that Mercedes tailored programs to cheat the specific demands of each evaluation, allowing the diesel engine of Mercedes-Benz models to run in an ultra-clean state, but only for limited periods of time, after which it was then switched into a so-called “dirty mode”.
The manipulation programs that are alleged to have been deliberately created by engineers are similar to those developed by Volkswagen and could drag the three-pointed star further in the Dieselgate scandal that has plague its German rival.
According to the information obtained by Bild am Sonntag, Daimler has developed a number of software programs suspected of being used to allow various diesel-powered Mercedes-Benz models to pass US emission tests.
Included is the “Bit 13” function. It sees the diesel engine switch to “dirty mode” once it emits 16 grams of NOx. This corresponds, it says, to the duration of the US highway test cycle.
Also suspected of being used is the “Bit 14” software function. It switches the engine into so-called “dirty mode” under certain temperatures and preset periods of time. This function is allegedly particularly suited to allowing cars to pass the FTP-75 warm test cycle.
Another software function called “Bit 15” is claimed to have been used during the US06 test cycle. It is programmed to switch off the SCR exhaust gas after-treatment system after 26 kilometres.
In addition, Bild says US investigators have also uncovered a further suspicious software function within the control system of various Mercedes-Benz models. Called Slipguard, it detects when the car is being tested on a rolling road and is claimed to influence the dosage of urea-based AdBlue solution within the SCR exhaust gas after-treatment system.
Information relating to the apparent Mercedes-Benz diesel engine emission manipulation software measures comes after news that the German Ministry of Transport is set to demand the German car maker issue a recall for diesel engined versions of its Vito commercial van due to discrepancies.
Sources reveal that tests performed on the popular Vito van reveal its SCR is programmed to reduce the injection of AdBlue to allow it to be filled during service intervals - thus reducing its efficiency and leading to higher NOx values than those claimed by Mercedes-Benz.
Mercedes-Benz is not commenting on the allegations of diesel emission manipulation.