[2011.2017.odyssey]

cold weather...

the cooling fan on the stereos/entertainment unit on these things squeals on cold mornings, once you unlock the door.
Mine has been doing it for years could be that.
same issue on the pilot.

2012 Touring w Nav - Stereo groaning / squeeling when...

So I finally solve my vibration issue and now this is happening constantly in the morning. The past 3 days... This had happened intermittently in the past, and seems more prominent the colder it gets. Functionality of the unit is unaffected. It sounds like the motors in the dvd or cd player...

www.odyclub.com

take a video of the noise, and general location its coming from, it helps a lot.

how long have you owned the vehicle? cold weather and poorly performing O2 sensor/heater will take a hit on the gas mileage.

 

[2011.2017.odyssey]

maybe its just a rattling heat shield on the back catalytic converter?