We have a 2010 chevy express that has an ambient temp sensor that works but no readout inside although all the lights in the readout are functional. Do some models not have this function? Can it be programmed?

Hello, it's a good question, but I think you'll probably need to ask this question of your local dealership service folks. They won't charge you to answer a question like this. My guess is that as equipped it's not something that can be "turned on" or "off", but requires specific equipment to provide that feature.