I have a fault reader, if you wish and haven't sold it yet, I don't mind the short drive over there to have a look at it for you.
And the offer has no bearing on your wheels, lol.
It doesn't sound like 'Limp mode' because you could still drive it, albeit below 50.
Just let me know if you want a hand, Mondys are generally great cars and I have no problem giving assistance when and where I can. :-)