How to read and clear codes (EML)
After purchasing the car and joining a few owner's WhatsApp groups, it quickly became apparent that I'd be dealing with various Engine Management Lights (EML) and almost certainly it would be in my interest to read these for myself. Reseting the car by putting it to sleep for 30 minutes (lock up, walk away) - as well as deep sleeping it by disconnecting the battery overnight - seemed to be common steps for existing owners.
To simplify this, a reader which can reset all the codes and clear any learnt values from the ECU seemed a very sensible step.
I got a generic Bluetooth adapter off Amazon (like £9) and an App on my Android phone (CarScanner).
Between these two, I've found nothing i cannot read or reset and clear. And I've encountered a LOT of spurious codes over the 4 years I've owned it so far!
Now don't get me wrong, this is no MDS (McLaren's own Diagnostic System) - so it has no advanced features and programming capabilities, but it can read and clear from all systems. Which is all I've needed to be doing so far.