2008 s80 4.4l low coolant warning is on and can't cancel. Replace coolant reservoir, new sensor, ran engine 20 minutes with cap off reservoir, removed both battery leads for 15 minutes and then held them together, replaced battery leads. Looks good for a few minutes until pressure builds and then it reappears. No leakage.
No codes display, any ideas would be great

Is there a fuse for this coolant level sensor and if so where is it located?