Hi, please try like this:
 
  1. Sign up and install the beta:https://play.google.com/apps/testing/uk.co.boconi.emil.obd2aa
  2. Open the beta (it will be an empty app)
  3. Using the Settings -> Apps -> obd2aa -> uninstall the app
  4. Immediately reinstall it from the APK you've downloaded from my website.
  5. Plug in phone to car when prompted select Android Auto. (no need to have the headunit reloaded server started at all)
  6. After making sure everything is working leave the Google Play beta channel so the app doesn't get updated to the empty version of the app