Pretty sure it is located right side of right foot well behind the right side panel. Mine was replaced a few times when I first got my RDX. My Eyes Free function enabling the use of Siri has also stopped working with the release of iOS 12. Acura released a service bulletin/letter at least a year ago stating they would no longer support that feature. Of course Apple isnt going to make sure their latest iOS will continue to function with the older interfaces such as the one in the RDX and Acura wont do anything about it although the vehicle is still under warranty. I was in the impression that the driver's controls where designed to maximise safety and security while driving, but the lost of Siri through the steering wheel control has made driving more dangerous without being able to use Siri. The alternative is to now use Siri on the phone while driving which make things too dangerous and is illegal here in Canada.

Every Acura owner should ask Acura/Honda to update their module software to continue allowing the use of Siri to keep our driving safe!