Well I bought a second hand Punto (year 2000). The key with the remote locking was in poor condition, so I bought a new plastic case and a new batery.
Now the led flashes but the doors don't lock; there is no answer from the central unit, it seems the central locking unit from the car doesn't recognize the emission from the remote key.
I look in the manual where the receiver in the car is but there isn't any reference to it.
Is there a special procedure in order to pair the key with the car unit?

PS:The key is working perfectly. I can open the door manually and start the engine as well.

Not sure whether it applies to this car, but on a non-Fiat, after changing the key battery, I had to keep button pressed for about 5 seconds until the LED flashed a couple of times. Can't remember whether this was in-range or out-of-range of the car. Wouldn't hurt to try, you never know!

red

Ok, thx.
I'll give it a try and I'll let you know.

I seem to remember something about holding the button down with the key in the ignition, though I think that was for a replacement fob rather than just replacing the battery and casing!

Well I tried both ways and nothing happen.
Thx both of you.
I'll pay a visit to my dealer to solve the problem.

Please post again with the solution (assuming your friendly dealer can advise) - I've seen others reporting same symptoms.

red

look in fuse box beneath steering wheel. Central locking unit is there, check wiring is not loose - worked for me

Well, here I am again.
I went to the dealer and he connected the examiner and we found out that the remote had the RF transmiter OFF. The IC U2741BN is dead.
Does any one knows where can I buy one? I googled but the only thing I found was tge datasheet.
I also buy a used working remote key in order to remove the IC. Does anyone have one?
Thx

Do you know which fobs you have? Have a look on eBay, they come up on there sometimes. I think you should be able to re-programme another key.

@ Scoobysnacks:
I know I can reprogramm as many as eight keys but Fiat wants £120 for a single key with remote in it .
I'm looking through Ebay but I only found empty keys.
Thanks any way

Well as I was googling about to find out where to buy the IC U2741BN I read the datasheet of the ic and found out that it needs a cristal to work.
I open my remote key and I noticed that on one side of the printed circuit there is something missing (I add a picture of it).
Can anyone with a similar remote confirm if there is a cristal in the place given in the picture?
If yes please give me the value it is printed in it.
Thx 1+

Well I can see nobody has got a Punto with remote key
You could give me a hand on this "little" problem.
Just peak a screwdriver and open your remote key and look if there a small piece of metal (Xtal) in the place given in the picture above.
Pleeeeeaaaaase

After all the help given about the missing Xtal I finally found out on a Portuguese Punto Forum that there is Xtal missing in that place. It's a 13,56Mhz smd xtal.
Thanks a lot guys for your help.

Whats up with all the post crying because no one answered there question, especially from people who haven't even contributed much or even at all to the forum.

No one is forced to take the time to answer questions on here, also there are very few puntos with the remote key, I bet very few members here have one, so how can they help more then they have.