The functionality of the software seems to have stayed the same. The GLK would reduce nitrogen oxide emissions during state tests, but would allow them to exceed the legal limits under real conditions.
Daimler said it would "fully cooperate" with regulators and "review the facts." However, there is no doubt that this looks bad for the car manufacturer. Apart from the fact that Daimler has caught the eye for a major recall, this indicates that the company has not disclosed the full scope of its emission practices in a timely manner. The concerns of the EU that German brands are conspiring with emissions technology are not exactly confirmed by this.