had to change the battery on S reg megane scenic, after reconnecting, the red light on the dash comes on and car starts, lights,indicators working ok, but the central locking doesnt work from the fob. there is a red light when the button is pressed but the car stays locked/unlocked, am able to unlock the car using the key
as an s reg that is the crossover period from one immobilizer system to another,as your car still starts i would assume you have the later which has hard plastic fobs as opposed to the rubberized earlier ones.hold the button down on the key untill the led stops flashing (5 secs or so)and then press it as normal,this should resynchronize it.obviously you need to be at the car.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.