How do I start my 2016 CX7 if my ignition device (proximity key) battery dies?
If you have the oval proximity key type with push button switch then hold the prox key next to/or push the button with the proximity key. This allows the switch to send enough power to the fob in order to activate the transponder portion.
If you have the card looking proximity key then you can try holding it next to the twist knob or if it is still not working you can remove the twist knob (there are 2 small buttons you squeeze). You will then be able to remove the emergency key from the card and use it in the ignition like the old days.