Why does the cylinder key lock just rotate all the way around without unlocking the car in my citroen c3 ?

well. why have only just one fob>?
the fobs die at 10 years old easy.
the buttons inside ,mine failed now 2times.
2015 to now. mine.
the buttons have switches in mine, gold plated
and the gold now looks like shot gun blasted. (under a microscope)
as in END OF LIFE worn out. all fobs do that.
or battery new is bad or battery in backwards
or battery clips bent or rusty
never have only one fob. (or land here x)

There is something called a BSI or BCM in those cars that tends to fail. The BSI is a computer that controls all those functions. Since I am not sure where you are located, use a search engine and put in the year, make and model and the term BSI or BCM and look at the results.

if the key wont unlock the door and the fob does then the linkage from the lock to the key has come apart, as the fob is actuating the electric motor , will need to strip out door panel to see where the connecting rod has got to

Your KEY will not unlock the Door? That has nothing to do with the FOB.

OR do you mean your FOB will not work at all?. If it is a PROGRAMMING ISSUE, you need to contact your Dealer

yes then when you get in turn key to number to and press the fob the locks should lock the door and the fob is rest.

I had the same problem.when I used my main key my car wouldn't start and I got the message "anti theft faulty". The key and the remote still unlocks and locks the doors and turns the lights on/off but it just wouldn't start my car. I was able to start my C3 by using the spare key. The main key is still faulty and if used brings up the same message.

Check on aliexpress for a silca key programmer V33.
This is a programmer for the ECU which you can use to reprogram the ECU to accept ID chip keys. If I remember correctly xantia uses ID46 or ID48 keys. You buy a used key, remove the circuit board and ID chip from it, put it into your own key, and then you have to program all your keys to be valid for the ECU. I haven't tried it on my own xantia, but have used it on another car with succes. It should cost around $80. https://es.aliexpress.com/store/product/New-Auto-Key-Programmer-V33-02-SBB-Key-Programmer-For-Multi-Brands-Brazil-SBB-Silca-V33/2341061_32845994522.html?spm=a219c.search0604.3.2.7e3dcc24iRDWLM&ws_ab_test=searchweb0_0,searchweb201602_6_10065_10068_10547_319_10891_317_10548_10696_10084_453_454_10083_10618_10307_10820_10821_10301_10303_537_536_10059_10884_10887_321_322_10103,searchweb201603_52,ppcSwitch_0&algo_expid=2203bafa-d1d5-4ba3-a1dd-d9f9fd1ed675-0&algo_pvid=2203bafa-d1d5-4ba3-a1dd-d9f9fd1ed675

I have had problems with a bad solder joint in the key fob. Mine would unlock ok but wouldn't lock. You can try taking apart the key fob and see if you can find a solder connection that looks cracked around it, then solder it up. Or you can just find a different one of Ebay and reprogram it when you get it. Please rate my answer so I am awarded points for it.

Retrain the fobs following the procedure in your owner's manual:


Once entering this procedure, programming the first transmitter erases all previous transmitters. You must program all transmitters.

Program one vehicle at a time. One transmitter could be programmed into other vehicles that are also on
program mode in close proximity.
1. Sit in the driver's seat.
2. Remove the ignition key from the ignition lock cylinder.
3. Close all vehicle doors.
4. Press and hold unlock on the door lock switch.
5. While holding the door lock switch in the unlock position, insert and remove the ignition key twice. Do
not rotate the ignition lock cylinder.
6. Insert the ignition key a third time leaving the key in the ignition lock cylinder. The ignition must remain
in the LOCK position for the rest of the procedure.
7. Release the door lock switch. You will hear three chimes. This chime feedback indicates that transmitter
programming is active.
8. Press and hold the lock and unlock buttons at the same time on the keyless entry transmitter for 12
seconds. You will hear two chimes. This chime feedback indicates that the transmitter has been
programmed successfully.
9. Repeat step 8 for the rest of the transmitters (for a total of 4 transmitters).
10. Exit this procedure by removing the ignition key from the ignition lock cylinder.

Here are the program instructions

1. Close the vehicle doors.
2. Turn OFF the ignition.
3. Remove the key from the ignition.
4. Press and hold the driver side door lock switch in the UNLOCK position.
5. Insert the ignition key into the ignition lock cylinder and remove the key. (Do not turn the ignition key in the lock cylinder.)
6. Insert the ignition key into the ignition lock cylinder and remove the key. (Do not turn the ignition key in the lock cylinder.)
7. Insert the ignition key into the ignition lock cylinder. (Do not turn the ignition key in the lock cylinder.) Leave the ignition key in the ignition lock cylinder.
8. Release the door lock switch. The vehicle will sound three beeps in order to verify the Program Mode has been activated.
9. Press the LOCK and UNLOCK buttons together on the keyless entry transmitter and hold until the vehicle beeps twice to verify that the transmitter has been successfully programmed (this take approximately 15 seconds).
10. Perform the previous step to program up to four transmitters (including your old ones).
11. Remove the ignition key in order to exit the Program Mode