My 2016 XC90 T8 Momentum is out of factory warranty not for long (odometer is at about 54,800 mi). Its check-engine warning went on about 2 weeks ago, then off for a few days, and then on since. I have lightly driven it and carefully observed the following symptoms or signs during the past 2 weeks:

1. The check-engine stayed on since the mid of December.

2. Under default hybrid driving mode and during transition from the electric motor-driving to the ICE-driving, the vehicle appears to have no driving power for 1 to 2 seconds until the ICE is fully geared up.

3. Battery charging and energy regeneration during braking appear fine but the system uses the battery power at a much slower pace than previously under normal condition (in other words, the vehicle tends to use ICE more often even if the battery has plenty of power).

4. Occasionally during the first few minutes of driving (when the engine is still cold), the rear passenger-side of the vehicle (left electric motor?) experienced a jolting motion and sound.

5. The vehicle does not hold up the AWD driving mode if set so; it changes to Hybrid mode by itself sooner or later.

6. Lately and frequently, the AWD mode or the “Off Road” mode became unavailable (became dark with a message “This mode is not selectable due to limitations”).

Overall, I suspect that the following part(s) may be malfunctioning:

1. The control system of the AWD driving mode or the switch control system from the electric motor-driving to the ICE-driving.

2. The real passenger-side electric motor (fixture is loose?)

I hope that those observations will help the local Volvo dealership service team to identify the underlining problem(s) quicker and more accurately and save service time and cost.