I lost one of month Fabia mark 2 keys so I bought a second hand fob I got a new key cut and put the appropriate new transponder in  I got it to work by suggested method. I

When I put it in Ignition it works but on the 3rd turn to start the engine the security siren goes off and will not start To stop this I take the key out and incert the original key  What's going on. I would be able to get in locked car and I suppose get the car home. Skoda Dealer employee friend says I need to get them to program it.--- Dougyboy

What did you mean when you stated you got it to work by the suggested method?

 

Additionally, do you mean the key opened and started the car a few times, then failed or opened, turned in the ignition, so the idiot lights came on, but then, on trying to fire up, that was when the issue started??

 

Transponders DO need coding but many people suggest they or others can do this with the necessary VCDS coding equipment or similar. I do not think it is either easy or perhaps even possible to code them, without this. 

 

I also don't get if the original key just stopped the alarm or if you can still drive/lock/unlock the car with it (Normal operation of original key). Sorry, the post was a little jumbled. I am taking a little leap here and saying I don't think English is your first language.

 

The new key started the engine running for a couple of times   About every 3rd time everything kicked off till I took key out and put an original key in the ignition     The new key opens the drivers door manually but I don't think it does it remotely Thankfully I would be able to get in the car.  The battery in the fob lights the red flashing display when I press the buttons

I have found that the unoriginal key is starting the engine because I have the original key nearby Put it a long way away and new key does not start engine just opens door manually. You are proberbly right they do need programming by a Dealer or someone with the right gear. The alarm did not go this time maybe because the door was unlocked normally Trouble is I have been quoted up to £130  just for the programming alone

If your "new" key is correct for the car - check PN, i.e. remote locking / alarm and the immobiliser you can get the car to learn the new key so that you can disarm the alarm and open the doors.

I had to get a new spare. From memory with the car locked, put the new key in the driver door lock and unlock the door while pressing the unlock button. If the car accepts your key you will see the indicator flashing.

The transponder can be cloned by any locksmith. They will simply copy the transponder from the existing key into the new one, so that effectively the car only knows one key - both with the same transponder.

Yes what you say my friend is absolutely right I have tried the door programs trick twice but it's not worked Last weekend I stared the car with the dud key but realized it was only doing so because the original key was on the passenger seat and was picking up the signal to start up from it.  Next morning my wife started car and reversed off the driveway and it cut out saying NO KEY. Later the alarm kicked off and hazards flashed. It took a while to stop it with proper key. The breakdown man said what I did should not have caused the cut out according to his Skoda dealer friend Disconnecting battery trick did not work. Local dealer wanted £164 up front for another key and up to 21 days wait and Green Flag would then have to get car to them. Just as my wife was ready to be taken to the dealer I thought it was an immobileiser problem and tried to start it again and it worked after 48hours. So now I keep that dud key out of ignition. I will try as you  say and see if a car locksmith can ptograme it cheaper.