xt660x Coolant Problem
 

I have an issue with my cooling system:
1. The radiator fan does not deploy - at the end of the trip the engine is still running but I can hear the coolant boiling in the radiator.
2. I ran the diagnosis and got an error 21. I have since replaced the coolant sensor and the radiator cap but the problem persists.
3. So far the overheating light has not lit up.

That sounds quite complicated. I'd pay a mechanic to look at it, or subscribe to this forum and download the manual for code diagnosis and service data.