2005 C4 key replacement

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tomaskriv
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2005 C4 key replacement

Post by tomaskriv »

My friend has 2005 C4. Most cars of this age have only one key. He managed to drop that single key on concrete and damage the immobilizer coil(?). Anyway smithlock came to his house and tried to fix that key. He replaced the chip and programmed that chip to the car. Unfortunately themote no longer works. It worked even after the key was dropped and was unable to start the car. Now key starts the car but does not lock doors...
Now he goth the blank key from ebay and want to program using Lexia. So we have few questions:
Can Lexia retrieve PIN from the car?
Can Lexia show whatblank key must be used? He noticed few different blank keys available online. Well just in case he has wrong blank key... The single working key that he has was repaired few times by the previous owners and now motherboard is covered with some black glue/resin stuff. Probably used to fix issues with buttons.

Thank you for all possible information.
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GiveMeABreak
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Re: 2005 C4 key replacement

Post by GiveMeABreak »

Can Lexia retrieve PIN from the car?
No. You will need the confidential customer code that is contained in the card that came with the car. If he doesn't have it - then he can get it from the dealer for a charge, plus proof of car ownership (vehicle registration document if in the UK), proof of identity, and proof of address.
Can Lexia show whatblank key must be used?
No to that question as well. This is a dealer-level tool, not intended for use by the customer, so it assumes you are already using official keys / replacement parts and not shopping off ebay :-D

Be careful of getting the correct fob - it has to transmit at the right frequency and use the right encryption protocol. Also be aware that ALL keys that will be used (including the current broken one) must all be programmed together in the same session (Lexia will ask you how many keys to programme). Any keys not programmed int he same session will be locked out and will no longer be able to start or open the car!

If he wants to know what the correct fob is, then you will have to get the VIN from him and post it here, then I can advise you.
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Re: 2005 C4 key replacement

Post by tomaskriv »

VF7**************[VIN obfuscated, can be read by forum staff]
2005 C4 1.4
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GiveMeABreak
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Re: 2005 C4 key replacement

Post by GiveMeABreak »

Ok, so if you Google 'Citroen 649097' that should give you some options. 649097 is the 3 button replacement fob part number.
tomaskriv
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Re: 2005 C4 key replacement

Post by tomaskriv »

Thank you for your time and information.
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Re: 2005 C4 key replacement

Post by tomaskriv »

One more thing:
This part number for the key shell or motherboard?
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GiveMeABreak
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Re: 2005 C4 key replacement

Post by GiveMeABreak »

That is the Citroen part for the complete fob including uncut key. That is why they retail at Citroen for £114.
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Re: 2005 C4 key replacement

Post by tomaskriv »

I've managed to program two brand new keys to the car. All working ok, engine starts and no more Antitheft Fault. The only issue now is resync the keys to the central locking. After programming I've disconnected Lexia and done this:
Key into ignition
Turn ignition ON
Within 10 secs press and hold LOCK button
Ignition OFF
Wait fot 15 secs.

Nothing.... Done same with both new keys. Maybe Lexia must stay connected to the car while this procedure is done?

Thanks for any ideas.
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GiveMeABreak
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Re: 2005 C4 key replacement

Post by GiveMeABreak »

Lexia doesn’t need to be anywhere near the car. The resynchronisation is done without Lexia as this is something the owner may need to do when replacing the fob battery.

If the remote functions won’t work then you probably have the wrong fob type. Aftermarket fobs vary in their quality as I’ve mentioned before and you probably have one that won’t work. The only reason the car will start is because the transponder chip has been programmed. You could wear that chip around your finger and the car would start with the key.
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Paul-R
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Re: 2005 C4 key replacement

Post by Paul-R »

When I synched the new key fob for locking on my C5 it didn't appear to have taken at first. It was only later on when I tried the buttons again that I found they worked.

Where did you get the new key from? A link would help.
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Re: 2005 C4 key replacement

Post by tomaskriv »

The key was purchased from Aliexpress. My father in low does not know how long he wants to keep this car do we went with the cheapest option.
I was unable to find exact key circuit board that we got with the car. So we purchased two diferent. Today I was able to program both to the car.
Witch part on the key board is responsible for locking function? Copper coil? Asking because the key that we got with the car was able to inlock the doors. After the locksmith added immobiliser chip (original was damaged after key was dropped) the lock unlock option was gone. Ibmean why original key is not syncing with the car? All three circuit board are looking different. And none is able to lock/unlock the car. Even the one that was able to do this before... Locksmith was unable to explain this to me. He said that key does not send signal even his equipment detected signal when you press buttons..... totaly lost now.
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Re: 2005 C4 key replacement

Post by GiveMeABreak »

Some possibilities:

1) The electronics of the Fob (your original) have been damaged (dropped or something similar).
2) Depending on options fitted, the Receiving unit or the High Frequency Antenna for the remote locking on the vehicle is faulty or there are problems with the electrical circuit.
3) Incompatible fob circuitry (new fobs).

If it is (2), then this may have been you original problem that prevented the old fob from operating the remote functions - so any replacements are still not going to work until the fault, if any, is found on the vehicle.

If you want to investigate the car side further, I can probably provide you with a circuit diagram to help troubleshooting, but will need the VIN of the C4 and you'll need to make a donation Tomas as we are now charged for access - but this will cover you for up to 2 years - details below:
A response to your question will require detailed vehicle information that requires you to have made a current contribution to the Forum.
Donate

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tomaskriv
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Re: 2005 C4 key replacement

Post by tomaskriv »

All I can hear now is a click like relay or something when I press lock button on one of the new keys.
How to know witch key to get?
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Re: 2005 C4 key replacement

Post by tomaskriv »

Correct me if I am wrong:
As far as I understand there are two systems. One for starting the car and another for locking/unlocking doors.
Programming needs to be done with Lexia. Syncing does not need anything. Sonfor example I can put into ignition one key and press the button on any other Citroen key inside the car and that fob will sync to the car. At the end I can have key for starting the car and key for unlocking the car. I mean it is not required that key must be programmed to the car in order to sync some circuit boar to be able lock the car...
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GiveMeABreak
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Re: 2005 C4 key replacement

Post by GiveMeABreak »

Not quite, but generally speaking: (the exact options you have will depend on your specific vehicle)

All the keys required to be used on the car must be programmed at the same time. Any keys not programmed in the same session are locked out of the BSI and Engine ECU.

The key fobs can have several functions, starting the car and remote unlocking and other functionality like boot release / guide me home headlamps, remote closing of windows etc.

The immobiliser system used to start the car relies on the transponder chip being recognised by an exchange of data between the unit inside the steering wheel that sends and receives the information to and from the BSI when the fob with the chip in is near to the ignition barrel which contains the transponder aerial circuit. The BSI talks to the engine ECU and if they are all happy, the engine is authorised to start.

The remote functions on a fob will only work if that fob has been programmed. The remote functions are sent via a rolling high frequency coded signal. In the vehicle, the signal is picked up by a high frequency aerial that usually runs down the central gearbox console. There will likely be an electronic control unit that the signal is fed into which then talks to the BSI. If the BSI authenticates the requests, then the corresponding action is authorised then the function (door opening, windows closing etc.) is carried out. If it is not authorised nothing happens.

Some of the older fobs had a separate transponder chip that sat loosely in the fob. This could be removed and replaced and then programmed. Some of the newer fobs have the transponder chip integrated onto the fob circuitry which makes this more difficult.

On the older systems, people who often needed a new key, just got a new keyblade cut and left the old fob on the key ring. As long as the chip was in close proximity to the ignition barrel it would allow the car to be started.

But for any fob, to be able to use the remote functions, the fob must be programmed and authenticated.