[ChevyGuy]

but sometimes the codes (P00B6 CODE) come back till I clear them again.

That's a sign that something still isn't right with one (or both) of those temperature sensors. It might be the sensor or the wiring.

 

[ChevyGuy]

P0068 indicates that after the car has been off for 8 hours or more, there's a greater than 20C/68F temperature difference between the Engine Coolant Temperature and the Radiator Coolant Temperature upon startup.