Daft question :-
Has your car had the Comfort 2 update done by any chance ?.
Depending WHEN it was done has identified as another route that the car could have been infected by a software glitch.
When the VIN number is checked, this may not identify your car as one recorded by the system ?.
My guess is the dealer will update the car to the very latest software on its next visit regardless !.
Their computer will show just what software you are running on anyway !.
MG Tech will advise that the software should be updated firstly.
This then should see you getting figures of around 448 - 450 volts after a full charge & balance and a range of around 160 - 162 miles on the GOM with all items turned off.
This will be in the default setting of driving mode NORMAL and Regen level 3.
The dealer may tell you that a number of home charges will be necessary to rebalance the pack over a number of weeks.
Therefore, you may not see the figures quoted above straight away.
They should also be able to tell you what the level of imbalance IS on the HV pack.
Good luck
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