Twice in the last 2 weeks I've had the "drivetrain malfunction" error message. Both times it was while moving in slow town traffic, roughly 3 miles from a cold start. Both times the message has lied when it said "performance is reduced". Over roughly 400 miles in between the two instances, the car hasn't run any differently to how it normally does.
It's MOT day tomorrow, and I had already asked my man to change the brake fluid and the fuel filter while he's got the car. When I get there, I'll ask him to run a diagnostic as well.
I'll update tomorrow.