You mentioned in another thread that the car had been sitting for a while. Since the 12V battery in a CT is relatively small and drains faster than a regular 12V battery if the car sits for a while for instance, I would include to check the battery health in your list.
Best would be to buy a new one so you know it's history and age.
This car can give all sorts of electrical errors, all dashllghts on etc. if the 12V battery is not in good health.
Mine read 75% health at the dealer when serviced, still in good health according to them, but a week later my car failed to start...
Changed with a new one and all was back to normal.