It could be a number of things. After 8 years it’s not uncommon to need to top up your coolant (especially if you haven’t been keeping an eye on it) It’s normal to lose a bit to evaporation.
First make sure your oil and coolant aren’t frothy/milky,. If either is....call a tow truck. Also have a look underneath for signs of leaks, likely near the water pump. If there’s a leak it will obviously need to be fixed.
If everything looks good, first guess would be that you have an airlock in your cooling system, assuming you didn’t bleed it when you topped up. Let it run with the rad cap off until the thermostat cracks open. You will see the coolant suck down into the rad, just start topping it up right away until it’s full. You should also feel both the upper and lower rad hoses get warm.
If the thermostat doesn’t crack (upper rad hose stays cold) you need to replace it.
If you get the air out and it still overheats, you might need a rad cap.
The list of possibilities goes on, but I like to start with what’s obvious, and what’s free before I start spending money. In my opinion, the electronic throttle sensor warning may not be related. I could be wrong though.
If anyone thinks I’m out to lunch please don’t hesitate to let me know. I haven’t been a mechanic for 11 years now so there’s a lot of skill fade.
