What could be wrong?

Hi, my name is Devin. I am an auto repair expert with the Car Genius team here at RepairPal. I'm sorry to hear you're having trouble with your Lucerne. If your engine is cold but the overheating and A/C shutdown warnings appear, it's likely a sensor issue rather than an actual overheating problem. The most likely culprit is the engine coolant temperature (ECT) sensor. If faulty, it can send incorrect temperature readings to the engine control module (ECM), triggering these warnings. It may be best to consult a trusted repair shop to diagnose this concern. If you need more advice, have any other questions about your vehicle, or would like to get connected to a RepairPal Certified shop near you, we have you covered. Give us a call at 877-913-1554, and we will happily help you out!