For the short term, there is a way to do this using the ignition key in the drivers door lock. You need to know the code for the car and have the handbook to tell you how to.
As to long term. If you have a one-button plip (fob) the handbook has a sequence for resync'ing it with the car which you could try.
If it is a two-button plip then then I'm afraid that it is rip to a dealer because it needs to be resync'ed using a diagnostic computer.
In either case the plip may be faulty.
t
October 2007