Porsche is under investigation by the German transport ministry and transport authorities to find out whether the brand was involved in the ongoing emissions scandal, according to German business magazine WirtschaftsWoche.

WirtschaftsWoche ('Business Week' in German) reported that insiders at Porsche tipped-off the authorities, leading to a full investigation into whether the company is implicated in the scandal.
It’s alleged that Porsche used a system that manipulates the car’s emissions based on how much steering input is detected; the standard emissions test requires no input, so if the system detects no steering input but lots of accelerator use, a special lower emissions mode is selected by the system.

A similar system was discovered to be in use by Audi, in which automatic gearboxes were believed to manipulate emissions by tweaking their action when a test situation was detected by the system. The subsequent investigation led Audi's then head of research and development, Stefan Knirsch, to resign from his position, which he had held for only nine months.