When I bought the WJ the seller only had one key, so I decided to get a key made up. A high st store cuts the keys and duplicates the code on a computer.
The new key opens the doors and starts the engine - but it cuts out after a few seconds and a symbol with a key appears on the gauge display.

According to the handbook you have to put the Two original keys in the ignition one after the other, then insert the new key to 'assign' it.

As I only have One original key is there something I can do to make the new key work ?

 

Not sure what kind of store you went to. You can clone those which is what it sounds like they tried to do. I would take it back to who did it and say it doesnt work. Either that or go to a locksmith that does transponder keys. To clone them the key they're using has to have a zero value. They may have used the wrong key. All the jeep, chryslers will start with an unprogrammed key then shut off in about 3 seconds.

 

Your WJ thinks you're attempting to steal it with a fake key and the SKIS system is activating.

My WJ owners manual states you need both original keys to program a new key. If you only have one, or neither original key, you need to go to the dealer to have any new keys programmed to your vehicle.

This explains it better. >->http://www.wjjeeps.com/sentry.htm

 

I don't even know where the nearest Jeep dealer is , I buy spare parts on E bay !.