C4 Fob Programming

[Ramc4]

For a new virgin key with remote fob do you use lexia the program the remote part or is lexia just used to program the transponder?

For example for 2 keys, one with remote and one without, do I program the transponders first with lexia, then program the remote by putting the key in ignition and pressing remote button for 10 sec?

[Hell Razor5543]

You will have to 'introduce' the transponder chip to the car first (make sure to do ALL of the keys, as any that are missed will be 'forgotten', will stop working, and will need another Lexia session to get them working again). Once the car is 'aware' of the chips it will be prepared to 'listen' to the remote locking functions of the keys (as part of this process is querying the transponder chip to see if it is on the list), including the process of activating the remote functions. Normally the Lexia is not needed to activate the remote function (as this would have to happen each time you replaced the battery in the fob).

[Ramc4]

You say you would need "another lexia session" yet i thought after any key has been programmed then it can't be programmed again, you would need a new virgin key?

[Hell Razor5543]

When a transponder chip has been programmed to a car it can ONLY be used by THAT car. When you are adding keys to a car (via a Lexia session) you need to do all of the keys (including any current ones) for the car to 'recognise' them all. If you forget to do a current key (say, you had lost it) it will be 'forgotten' by the car (but, as it has been coded to the car, it cannot be reprogrammed), so if you find it again it won't work at that time (this means that, if a key were stolen and you ran a key Lexia session that stolen key will no longer start the car (but I DON'T know if this will disable the remote locking function)). However, if you find the key again you CAN (via another full key Lexia session) add it back into the list of keys the car will 'remember' and it will work again with the car it was programmed to originally (keys cannot be transferred between cars).

[Ramc4]

Thanks good answer.

So should I treat the fob programming as a different"session" to the key programming.

In other words I program both the keys via lexia then I sync the fob by pressing the close button while the fob key is in the ignition?

[Hell Razor5543]

Yes. In order for the car to accept the fob is valid (to use the remote functions) it has to already 'exist' in the memory of the car (the transponder chip details, that is). As I understand it (for security reasons) if a button on the key fob is pressed (with the key in the relevant position in the ignition) the car 'reads' the transponder chip first. If that chip 'exists' in the memory the car is 'prepared' to 'listen' to the remote functions. However, if the car does not 'recognise' the transponder chip it will not acknowledge it when the buttons are pressed.

[GiveMeABreak]

There are 2 parts to this - programming the transponder chips contained in the keys (with and without a fob) and the other part is synchronisation.

You should only need to programme the keys once, but may have to synchronise the keys every time you change the battery or if the number of offsets is exceeded (usually when the remote locking is triggered over too greater a distance).

You need Lexia to programme the keys, but do not need Lexia to resynchronise the remote fobs.

[Ramc4]

Finally got this cleared up. Thanks a lot.

[GiveMeABreak]

No problems. This is the resynchronisation procedure for your C4:

1. - Switch off the ignition and take out the key
2. - Wait 1 minute without pressing the buttons of any remote control
3. - Place the key of the high frequency remote control to be synchronised in position "ignition+"
4. - Within 10 seconds, press the locking button for 5 seconds
5. - Switch off the ignition and take out the key
6. - Repeat the procedure with the other keys from point N°3, otherwise move on to point N°7
7. - Wait 30 seconds, the remote controls are synchronised

Carry out a locking / unlocking test of the vehicle’s doors and tailgate.

[GiveMeABreak]

He's already got it James.... I've removed the post as it is unnecessary and repeating information.

viewtopic.php?p=625227#p625227.

[Ramc4]

It says it's for a Grand Picasso so you'd assume it won't work as the have a c4 coupe (LX) 2006 but I'm 99% sure it's the same transponder ID46 running at 433mhz.

So if this wouldn't work then why not?

https://www.ebay.co.uk/itm/For-CITROEN- ... 0167.m2940

[GiveMeABreak]

Please keep to one topic for the same issues.

[Ramc4]

Sorry. Will do.

[Hell Razor5543]

Most manufacturers (car makers included) will use components across a range of suitable products, so the key for a C4 may well be the same design as a key for a C5, for example. The changes that then make them unique to a specific vehicle are the cutting of the blade and the 'introduction' to the vehicle.

[GiveMeABreak]

That's not strictly true. The frequency and the encryption are also important.