Hi. I’m not too sure if this is the right place for it but I really couldn’t find a palace for advice. I have a 2018 ford focus st line, 1.5l 3cyl turbo. A couple days ago the wrench warning light came up and disappeared when I’d restart the car, I thought it wasn’t too urgent so I didn’t really book it in for anything. Then yesterday, as I’m driving, the whole electronic system began to malfunction and I’d lost power steering. It comes up with steering assist malfunction-service required, esc malfunction-service required ect. Had a look at it on an obdII reader and found the code U3000:66 8a, told me it was something to do with the power steering module. I’m wondering if this is the type of malfunction that requires me to change the whole steering rack etc. thanks 

There's a good chance this is simply a low battery issue.  That's the first thing to check.  

Mk4 Focus racks aren't a common failure, so I'd be checking wiring & plugs after battery myself.

When my alternator went on my mondeo first I knew of it was a loss of power steering at a busy junction outside a hospital (nicely engineered ford). Definitely check battery and alternator first. Good luck

Did you get it sorted i have the same issue battery caused the issue but changed the battery and fault hasnt gone