l have just bought a s-reg citreon xsara 2.0 vts and l was told that the key fob for the remote locking needs a new battery. l fitted one, it worked once and then stopped working. any ideas.
i only have one key fob.

sometimes keyfobs need to be reprogrammed when the battery is replaced. this is done by holding the two key fobs together, and then holding down unlock on both for about 30 seconds, l dont now if that works with citroens but it does with most cars.

It might need recoding, ask your nearest Citroen dealer. The parts department would be a good place to start.

The plip may need recoding, However, since it worked once l would tend to suspect that the plip itself may be faulty, especially due to the age of the car. If this is the case then u will have to buy a new plip from ur dealer & get them to program the new plip for you.

But below is the procedure for recoding a plip as the car does not need to be hooked up to a computer for recoding plips, but it does for recoding the actual key blade. So give this a try.

Wait for 1 minute without pressing anything, insert the key into the ignition, turn the ignition on & within 10 seconds press & hold the locking button for 5 seconds, remove the key & DO NOT press anything for 30 seconds.
If u press anything the plip will desynchronize & u will have to wait 1 minute, then ur further 1 minute before trying again.

Holding 2 plips together has never worked for ANY Citroen.

Sometimes these cars can be a pig to accept a recoding procedure though, so try that a few times & if it still does not work then open the drivers door, wait 3 minutes minimum & disconnect the positive terminal of the battery. Then short the positive LEAD u have taken off to the negative battery terminal (DO NOT SHORT THE BATTERY POSITIVE TO NEGATIVE ONLY SHORT THE LEAD TO NEGATIVE)
This will discharge any current stored in capacitors in the ECUs & wipe the memory regarding the plip code.
Wait 5 minutes & reconnect the battery (ignition turned off)
Wait a further 5 minutes & try the plip coding procedure from above again.

If none of this works then go to ur Citroen dealer & buy a new HF plip.