Overheating

Are you going by the gauge in the instrument cluster? Those are notoriously inaccurate and are only good for observing when something abnormal is occurring. 220 degrees is not abnormal on many GM engines. If the radiator fan cycles on at times, it is working.

If you want to know the exact coolant temperature, you need to use a scanner to view live data and see what the Engine Computer is seeing.

Even up to 228 or 230 would be normal.

GM commonly runs their engines at very high temperatures. Water boils three degrees hotter for every pound of pressure it's under. With a 15 psi radiator cap, that brings the boiling point up to 257 degrees. It is also why people can be scalded when they're under the hood with a ruptured radiator hose or when they take the radiator cap off too soon. With the release of pressure, the water boils instantly and turns into steam. As it escapes, pressure keeps going down and the remaining water boils even faster.

The highest temperature I've ever run into so far was 226 degrees. Other manufacturers turn their radiator fans on by around 210 degrees.