Old spare key not starting engine

Question

I have lost my spare key a while ago. I went to the mechanic and asked them to get a new one. They told me that I also need to bring my current main key as programming a new key will invalidate the old ones, so they have to programm them together. My mechanic also told me that if I find the old spare key I will still be able to use it, but the remote opening will obviously not work.

So far so good, recently I did in fact find my old key again. I was wondering if it works and as expected it would not open the doors without turning the key in the door lock. I was able to open it by turning it in the lock.

When trying to start the car with this key it did turn the starter motor, but no ignition was happening - i.e. the engine does not start, it only turns from the starter motor. I was googling this and realized that this seems to be common, however it did contradict what my mechanic told me.

My question is: How does this work? Is there an RFID connection between the ignition cylinder and the key? This is an old 2010 Mitsubishi Outlander, so the key isnt really that "smart".

Answer 1

Keys (or just fobs for pushbutton starting) are tied to the vehicle. They are programmed into the computer through whatever method the manufacturer sets up. To identify the key, there's an RFID chip in the key, which is interrogated by an transceiver in the vehicle. If the chip in the key does not match the ones stored in the computer of the vehicle, then the car won't start. The vehicle can do this by disabling the fuel, ignition, or both.

When you went to get the new key "identified" by the vehicle, the process is done first by wiping all keys from the vehicle memory. Then, the vehicle relearns all keys which will be added back in. The original key is needed to start the process. If it wasn't done that way, anyone could just rekey the vehicle on a whim and away your car goes off to a new home thanks to a would be thief. Your old key will not work now because it was wiped when the new key was added. You could take all three keys back and get them all added back into memory (in most cases), if you wanted to. It would cost you whatever it costs to do that.