Hi, I have just registered today after I was after some help about a different issue for my 97 Laguna RT 2.0. I got the help I needed, hence it is good to pass some help for you.
A common problem with Lagunas and other models of the same age of my car is that from time to time the immobilizer dies out. One manages to enter in the car, turns the key and hears just a click... and all electrics die out.
My solution was the following:
1. Turn key off and remove
2. Disconnect the battery from both
wires (only one does not work)
3. Wait 5 minutes (yes 5 minutes at least)
4. Connect both wires
5. Press the fob and see if the doors open/lock - if not repeat steps 2 - 4 leaving the battery disconnected a bit longer.
6. Turn key on and drive away.
99% times immobilzer is reset and all should be ok.
Trust me, it works. You would not need the dealer, codes, by passes or expesive equipments.
I note that the immobilizer plays up in waves.... for example during one year it never goes wrong... then in one week it fails 4 times. Then again for many months nothing happens. I also note that the immobilizer may go funny when there are massive thunder storms close by.
The above procedure has never left me stranded. I hope it works for you. I am sure it will.