so new car working great till today here's what happened.
wife parks car locks it by pushing lock on key fob.
returns to car forgets to deactivate alarm.
opens trunk using key due to not operating from electric.
alarm goes off she hits buttons on fob and do nothing.
puts key in drivers door and unlocks alarm quits.
then car would not start only cranks but wont start.
try's about 10 times nothing. tell her to try new key I had made.
she does and car starts no problem.
drives to house shuts off and starts fine.
uses original key and it works fine also.
just little worried now don't want her getting stranded.

 

There are two microchips in a key fob and both have to be registered with the car's electronics.

One is for the remote opening / locking / boot / headlamps ... the four buttons on the fob. This chip is powered by a button battery in the fob. It sounds like that one is working okay.

The other is a chip a bit like the ID chip the vet injects into the neck of your cat or dog; each chip has a unique number. It's powered by induction from coils that are around the ignition lock. It sounds like this one either isn't working or isn't isn't registered to the car ... maybe.

As you have two keys that work you should be able to re-register them and register the semi-duff one without having to use a Mongoose/SDD computer.

The procedure has been described a number of times here. I'll search for it and post a link if I find it, unless someone else beats me to it.

Edit: Yeh, try post #37 at https://www.jaguarforums.com/forum/x...q-87749/page2/