Mercedes-Benz has equipped various diesel models with software that may have helped them pass emission tests, according to a report published by German newspaper Bild am Sonntag.
The report, citing information Bild am Sonntag says is contained in a US Department of Justice investigation, claims engineers from Mercedes-Benz parent company Daimler developed various software programs that allowed unspecified diesel models to pass US emission tests through the manipulation of the engine and its selective catalytic reduction filter.
The software programs are alleged to have been tailored to the specific demands of various cycles in the US emission testing procedure, 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 to a so-called “dirty mode”.
The manipulation software programs allegedly used by Mercedes-Benz to allow its diesel models to pass the US tests could be similar to those developed by Volkswagen and threaten to drag it further into the Dieselgate scandal.
According to the information obtained by Bild am Sonntag, included among the software programs alleged to have been developed for diesel-powered Mercedes-Benz models 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 to “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 16 miles.
Bild says US investigators have also uncovered a further suspicious software function within the control system of various Mercedes-Benz models. Called Slipguard, it reportedly 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.
The allegations come after news that the German ministry of transport is set to demand Mercedes-Benz issues a recall for diesel-engined versions of its Vito commercial van due to discrepancies.
According to sources, tests carried out on the Vito reveal its SCR filter 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.