mintae

My car is a Mercedes-Benz CLA250 2020 model year, and the turbo booster error P029921 has been confirmed. The symptom is that the boost does not go up at some point while the turbo booster works, and when the engine is reset, the turbo boost rises again. And on the uphill road, there is not enough strength, so it is impossible to climb on a steep incline.

NovaOne

Could be a variety of issues, such as a faulty bypass valve or blow-off valve (not sure if the C118 has one of these since sometimes the design recirculates the pressurized air). In any case, pray that there is a leak somewhere, not that the turbo itself is faulty.