Here's a quick DIY for installing/swapping heated seats into a 2017 Mirage SE. This should apply for other Mirages, but take a look at yours first before attempting. I picked up a set of heated seats from a wrecked 17' G4. My 17' had all the harnesses in place and everything was plug and play. One way to check to see if your wiring is present is to look under each seat and see if there's a white plug just chilling in a white clip under the seat not plugged into anything, after that, pull up the tray ahead of the shifter and see of there's a plug under there tucked down to the left held in with electrical tape. If it has the plugs under both seats and under the shifter tray, then these steps should work.
Also, if you don't want to swap seats but install pads in your current seats, and have the plugs intact, you could follow these instructions too and hit the ones that apply to your set-up
Seats with Heated Pads in them
Heater Seat Switch - Part No: 8610A114
Console Tray - Part No: 8011B055ZZ or 8011B056ZZ
Power Seat Relay - O-Reilly Part No: 25-0137
1. Swap the seats. On the passenger seat, there are a total of three sensors that need be unhooked. Then remove the 2-14mm nuts in the front and 2-12mm bolts in back. Remove passenger seat. On the driver's side, there's also three sensors that need to be unhooked. Remove the same 2-14mm nuts and 2-12mm bolts, and remove seat.
2. Install other seats. Plug in the four plugs into the bottom of the passenger and driver seat. Tighten down the 14mm nuts and 12mm bolts. Seats are now installed.
3. Pull up on the shifter tray, install the switch and plug it into the switch plug under the tray, and reinstall tray.
4. Put the 20A relay in the blank spot in the location in the relay box. I bought one from O-reillys. Part number 25-0137.
5. Test the operation, they now should be working. They are quite warm btw.