It is possible that you have a bad thermostat. It's rare but it does happen.
Problem is checking the coolant temperature as it comes out of the engine.

The dealer SHOULD be able to check that.


My 2¢

 

On CX5 a bad thermostat would cause warm up cycle issues which would generate a DTC. Among other things the warmup cycle would be disrupted and the AFR would be off causing high EGTS and a rich fuel mixture, hence causing a DTC. Yup this is modern and wonderful world we live in that vehicle computer's (ECU/TCM/PCM etc.) are rather "intelligent" to use the word lightly. LOL Besides there is nothing yet that I see that is any problem in anyway. Like I said a simple temperature test of the air coming from the vent can tell. I get customers ALL THE TIME claiming their vent air is not warm with nothing wrong with any system. Now if were a car of the 80's or older sure maybe then you could say needs more investigating? But then back then simply placing a piece of cardboard in front of the radiator in cold cliemnts solved most of the creature comfort complaints LOL.

As for checking the coolant it is sooooooo easy those BIG radiator hoses one will be warm or hot the other cooler. LOL But you can use a handheld Thermoset reading devise to see exactly the temperature. Or get creative and use one of those kitchen thermostats just to get a rough idea of temperature comparison.