Mitsubishi Repair Problems? Ask a Mechanic for Answers ASAP
Unfortunately there is no alternative.
The current keys which are lost still work, and if found by somebody else gives them the chance of theft of vehicle.
When the new key is made, the lost key will be disabled in the programming sequence.
$600 is cheaper these days than some of years back, where modules had to be replaced as well.
Hope this helps
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I hope my advice has been of assistance to you.