XSeries-forum

I'm stumped with this one, I guess the key itself may have become faulty......

We have 3 keys for the 4.8, they have always worked fine and I have tried to rotate them so the battery doesn't run down - its the old diamond style key where replacing the battery is a bit of a faff and meant to be impossible.

2 of the three now work fine, the other one refuses to lock or unlock the central locking from the fob, but does start the car if I enter the vehicle using one of the working fobs.

Any ideas as to what I could do to get it working properly again or what might have gone wrong?  As the other keys work perfectly, I think I have ruled out a car problem with antenna or fuses etc. 

Could be the battery starting to go so not enough power to send the signal to unlock/lock the car or possibly the transmitter itself.

You could try re-initialising the key with the car (can't remember the process again off hand as it's been sometime) but that would mean having to pair all the keys again.