What brought the GLE in
The owner noticed the GLE felt slower than usual, especially when pulling away from a standstill or merging on the expressway. The engine check light came on shortly after. It was not a dramatic failure: the car still drove, but the turbo was clearly not building boost the way it should.
For a GLE with a turbocharged engine, reduced boost means reduced power. The car runs in a kind of limp or reduced-performance mode while the engine management system registers a sensor fault and protects the turbo from further damage.