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Robert, UK Qualified Car Technician
Category: Car
Satisfied Customers: 4716
Experience:  Fully qualified / self employed garage technician in the UK
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i have replaced the key fob on my C3 Desire fitting the oriignal

Customer Question

i have replaced the key fob on my C3 Desire fitting the oriignal key into the new fob but i can't get it to work. I have repalced the battery and tried reprogramming it but still no luck. Can you help plese
Submitted: 3 years ago.
Category: Car
Expert:  Robert replied 3 years ago.


How do you mean its doesnt work? Doesnt operate the central locking - Or fails to start the car?

What was the initial reason for replacing the fob itself? and was it working prior to transfering over?

Customer: replied 3 years ago.

The remote key fob was working alright but the case was broken. I fitted the original car key to the new case and fitted a new battery. Since then I cannot get the remote to open or close the doors but the engine starts alright.

Expert:  Robert replied 3 years ago.


Ok normally the procedure is as below..

Sit in the drivers seat with all the keys and all the doors shut, radio off, no lights, everything OFF
Insert a key into the ignition
Turn ON the ignition
Press and hold the LOCK button on the key for TEN seconds
Turn off the ignition and remove the key
Insert the next key and repeat the procedure
WAIT 1 minute, do NOT switch anything on.

When the 1 minute is up, open the drivers door, exit the vehicle, close the door

Test the keys each lock and unlock the doors.

If that fails to work then try reseting the BSI as below..

Open the drivers window and the bonnet.
Close all the doors, switch off everything, like the radio, phone charger etc.
Remove the ignition key via the open window
WAIT 10 minutes
Disconnect the battery.

(change the battery at this point if this is required, otherwise WAIT 30 seconds)

Reconnect the battery,
WAIT 1 minute
Keeping the doors closed, lean in via the drivers window
Switch on the 'ignition' (Don't start the engine)
Switch on lights (Dipped, normal driving lights)
WAIT 30 Seconds
Start the car / switch off and check central locking

So as above give those two procedures a try

Customer: replied 3 years ago.

I am doing that now and will reply when I have finished it.

Expert:  Robert replied 3 years ago.

Hi..there..thats fine

Customer: replied 3 years ago.

I had already tried the first procedure as I knew about it but without success. However, I have tried both procedures exactly as you described and I'm afraid neither worked. Still nothing happens when I press the remote buttons.

Expert:  Robert replied 3 years ago.


Doesnt sound right.. the last procedure is the official reset of the body control system or BSI that controls the central locking and often solves key/central locking issues..are you sure the new battery you have put is the correctly seated/isnt actually flat anyway.. not really uncommon to find that with new ones..where i would suggest actually getting the battery from a known good motor parts supplier or the dealer even..the problem really is that the cars bsi/comms isnt seeing the key thats why the central locking isnt responding..normally as i say those procedures above should work to solve that..the next step id say is to see if the key is actually transmitting - you need a special tool to do test the signal from the key and how strong it is..most id say autolocksmiths might have that..however if worked before and all you did was transfer the board/battery/transponder into the new case then it should work with those procedures above..what id do is maybe try another battery just incase and try it again..

Customer: replied 3 years ago.

That's all i have done. The battery is fine, I just bought it today from Halfords and I also checked it woith a voltmeter and it is giving off 3.25 Volts.

I will try the procedure again and see if that works. I'll let you know what happens.

Expert:  Robert replied 3 years ago.
Customer: replied 3 years ago.

I have tried both procedures again very carefully and the fob still cannot open or clsoe the door.

I will try an autoplocksmith tomorrow if you can't offer any further suggestions.

Expert:  Robert replied 3 years ago.

Hi..there..ok i have checked my other autodata database and it the same procedure too.. Like i say normally those procedures should work aswell as what no doubt detailed in the owners guide..i would if it was me get it on lexia 3 diagnostic to see if the problems on the car or the actual key itself..where then if was the key say then another would have to be sought/programmed to the car..

Customer: replied 3 years ago.

Thanks for your efforts. I'll do that tomorrow and hopefully that will sort it out.

Expert:  Robert replied 3 years ago.
Hi..there.. no worries..let me how you get on anyway..