Hello I am new here. I have a 2015 ct with 98k miles on it. My ct at first started rattling bad and then I noticed my coolant was starting to disappear. So I talked to my mechanic and he said if your coolant is disappearing it's a bad head gasket. So my question is. Has anyone replaced the engine on a ct? If so. Is there any reprogramming to do once you replace it? Thanks for the help in advance.