The software's functionality appears to have remained the same. The GLK would reduce nitrogen oxide emissions during government tests, but let them rise above legal limits in real-world conditions.

Daimler said it would "fully cooperate" with regulators and was "reviewing the facts." There's little doubt that this looks bad for the automaker, though. In addition to putting Daimler on the hook for a larger recall, it suggests that the company didn't reveal the full scope of its emissions practices in a timely fashion. This won't exactly assuage the EU's concerns that German brands were conspiring on emissions tech.