2017 DODGE CHALLENGER Forward Collision Avoidance Adaptive Cruise Control Problems

2017 Dodge Challenger GT, very well maintained. About two months ago, I would hear chimes but no messages popping up. A few days after this started happening, I am driving on the parkway and then ACC MODE flashed on the message center behind the wheel, but then went away very quickly - I could not see what else the message was trying to indicate. This happened several times on the trip home from work. Otherwise, the car drove without an issue. A few days later, on a Sunday, I am driving and the check engine light comes on. I bring it to Auto Zone and get a reading of thermostat erratic. Bring it to the mechanic the next day on Monday, who gets the same reading. He calls me to say after replacing the part, it was "throwing really weird erratic codes" & asked if I would approve a temperature...