I had a spare remote that I was listing for sale, but instead- bought another i-MiEV that was missing the fob!
With the conspiratorial support of my dear old dad, a retired petroleum engineer who's been geeking out on his freshly-installed solar array, we bought a 2012 ES with quick charge and 43k miles that was owned by a friend in the Seattle EV Association. To get my spare remote sync'd up, I set appointments with two different dealers, both of which sold the i-MiEV for its entire run. The first one worked on the car for 1 hr 15 min before declaring that they 'don't have the updated equipment' to do the reprogramming...... The second dealer still has their original i-certified tech, who called me back into the service bay after 1/2 hr to say he was having no luck and show me the procedure! No special tools required, just a special sequence of key turns and button pushing. He was nice enough to print off the procedure from two different sources (slightly different wording) and show me a YouTube video of the procedure. Sure enough, after a couple of attempts at home, with one set of hands on the ignition key and another on the keyfob, we got it working!
A used remote can definitely be reprogrammed for a different car, but will only serve one car (losing its previous link with each reprogramming).
For resourceful i-nthusiasts, up to four remotes can serve one car!
It may take several attempts to reprogram.
Though the old remote battery seemed fine, we didn't see success until it was replaced (perhaps that 'hard reset' helped).
Here's a link to the procedure: https://www.mitsubishitechinfo.com/data/TQ/2012/54/HTML/M154470450001000USA.htm
And here's the video: https://www.youtube.com/watch?v=UFF89jBMTIk
Here's the text of the procedure.
Up to four MiEV remotes can be registered in the EV remote-ECU by operating the MiEV remote and the electric motor switch.
note When a MiEV remote is registered, all the information on the previously registered MiEV remote(s) will be erased. Therefore, if an additional MiEV remote is registered, all the MiEV remotes (including the previously registered ones) must be registered again.
How to register MiEV remote
Switch the MiEV remote into the registration mode according to the procedure below. (This operation is necessary only when the MiEV remote(s) are registered again.)
Press the power/communication switch of the MiEV remote for at least one second to power on the MiEV remote.
Press and hold the MODE switch. Then press the power/communication switch and then the DOWN switch without releasing the MODE switch.
All the LCD indications on the MiEV remote illuminate, and then it enters the registration mode.
The MiEV remote will be powered off and exit from the registration mode when 30 seconds elapse since the last operation.
If the system does not proceed to the registration mode, the MiEV remote may be defective.
Switch the vehicle into the registration mode according to the procedure below.
Move the electric motor switch to the LOCK (OFF) position.
Wait for three to five seconds after the electric motor switch is turned from the LOCK (OFF) to the ACC position. Then turn it to the LOCK (OFF) position.
After carrying out item (b), turn the electric motor switch from the LOCK (OFF) to the ACC position within 10 seconds, and then turn it back to the LOCK (OFF) position again.
The vehicle enters the registration mode by repeating item (c) four times.
note To check whether the vehicle has entered the registration mode, try to communicate with the vehicle by using the MiEV remote (which has not been in the registration mode). If the vehicle does not respond to it ("ERROR" is displayed on the MiEV remote LCD), the vehicle has entered the registration mode. If the MiEV remote receives signal from the vehicle normally, it has not entered the registration mode.
After carrying out step (2), press the power/communication switch for at least one second within 15 seconds. Now all the LCD indications on the MiEV remote must flash and the tone alarm must sound.
When step (3) is carried out within 15 seconds after step (2), the vehicle will exit the registration mode.
If the MiEV remote LCD does not flash, or the tone alarm does not sound, the MiEV remote is suspected to be defective. (If the tone alarm is disabled, it will not sound.)
After carrying out step (3), all the LCD indications on the MiEV remote must illuminate and the tone alarm must sound to inform that the MiEV remote has been registered.
note When all the LCD indications on the MiEV remote do not illuminate and only the ERROR indication flashes, the vehicle may not enter the registration mode. Repeat from step (2).
If several MiEV remotes must be registered, carry out step (4) and then repeat steps (1) and (3) within one minute.
When the electric motor switch is turned from the LOCK (OFF) to the ACC position after registration, the registration mode will be exited. Alternatively, the registration mode will be exited if four units of the MiEV remote are registered or at least one minute elapses after the MiEV remote is operated.
Check all of the registered MiEV remotes for proper operation.