C4 Fob Programming

[Ramc4]

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

Ah, so it could be different encryption, never thought of that. If I set lexia for 2 keys to be programmed and it turns out this eBay is not compatible, what will happen. Will the first good key still be usable?

[GiveMeABreak]

My first guess it that it won't be able to be coded - purely because it won't be handshaking.

Your VIN may help me determine the type you have. You don't need to get int he car - the VIN is on the outside of the windscreen glass, lower passenger corner. 17 Alphanumeric.

[Ramc4]

My first guess it that it won't be able to be coded - purely because it won't be handshaking.

Your VIN may help me determine the type you have. You don't need to get int he car - the VIN is on the outside of the windscreen glass, lower passenger corner. 17 Alphanumeric.

Got vin from vc5.

VF7**************[VIN obfuscated, can be read by forum staff].

[GiveMeABreak]

Ok, so your fob part number (uncut) is part 649097 (three button fob).

As in here:

http://www.car-keys-online.com/product/ ... 49097.html

£157.79 inc UK 20% VAT is the price from Citroen.

[Ramc4]

Ok, so your fob part number (uncut) is part 649097 (three button fob).

As in here:

http://www.car-keys-online.com/product/ ... 49097.html

£157.79 inc UK 20% VAT is the price from Citroen.

Thanks. Yeh I knew it wasn't cheap hence why I'm trying to do it this way.

So you don't think these eBay keys/fobs for £10 will work or is it too difficult to get an exact match?

I'd have to email the seller and get exact part numbers etc?

Also would you be able to get the code for diagbox from my vin, I think it's an RDO number or something, needed when installing/activating?

[Hell Razor5543]

If you are talking about the security code you can normally only get it from a dealership. However, if you are talking about the RPO number there will be a label (normally stuck in the driver door space) with various numbers. One will be 5 numbers and 2 letters long (for example, 10042CJ). This is the RPO number, and can be used to find out when the car started to be built, and in which factory (the numbers are date related, the letters are the factory code).

[Ramc4]

Same key on aliexpress for $5.81.

[GiveMeABreak]

Ok, so your fob part number (uncut) is part 649097 (three button fob).

As in here:

http://www.car-keys-online.com/product/ ... 49097.html

£157.79 inc UK 20% VAT is the price from Citroen.

Thanks. Yeh I knew it wasn't cheap hence why I'm trying to do it this way.

So you don't think these eBay keys/fobs for £10 will work or is it too difficult to get an exact match?

I'd have to email the seller and get exact part numbers etc?

Also would you be able to get the code for diagbox from my vin, I think it's an RDO number or something, needed when installing/activating?

1) Ebay sellers are notoriously well known for selling crap fobs that don't work - plenty of posts here from people that have wasted time and money on ones that never work - your choice, but expect rubbish for that price.

2) Your RPO is only needed when you launch Lexia to ensure your build date is identified and this for your car is: 10796

3) You will need the confidential code from the dealer if you do not have it or the confidential card that came with the car. This cannot be obtained from the diagnostic equipment - it is held by PSA on their servers. They will issue it to you on proof of identification, vehicle ownership etc.

[Ramc4]

Thanks again.

If I do buy and try to program the eBay fob key along with the key I'm getting from the dealer, after telling lexia to program 2 keys, should I try and program the eBay key first and if the ecu rejects it then start a new lexia session and just program the dealer key?

I assume starting a new session consists of pulling out the obd2 cable and starting diagbox again, in other words how would I cancel the session of programming 2 keys?

Also what's the range of RF signal from the ignition transponder, for example if I'm programming 2 keys then i assume the second key has to be sufficiently far away from the ignition so the transponder doesn't attempt to communicate with the transponder in the ignition while I'm programming the first key?

[GiveMeABreak]

For Programming, the key needs to be in the ignition barrel itself, just don't have the other one on the same key ring.

The programming will either work or not. You have to tell it how many keys to programme before starting.

Never pull the OBD out of the port during a live session - you risk bricking any one of the ECUs by leaving it in an unconfigured / partially configured state. Always back out of the procedure using the functions in Lexia. Complete the programming procedure entirely. The Dealer fob (I assume you have one from the dealer) should code perfectly. If the cheap one doesn't, then nothing lost - bin it. But if you buy another fob, you need to repeat the process again with your working fob / key and the new one.

[Ramc4]

Thanks. Been great advice. I've spent a good few days trying to work out what I needed to do but this forum has sorted all that out.

[Ramc4]

Got the dealer key + code today, the key is very stiff in the door had to thump it in and can see the cut edges starting to smooth after one use in the door hence I need a remote as will ruin the key very quickly.

So again, if I risk getting the cheap eBay remote key which I've determined has the exact same transponder so it should code and start the car however I'm doubting whether the remote part will work.

But if it turns out that the transponder isn't compatible with the car also and I've set diagbox to program 2 keys, what would I do in diagbox, just press cancel if there is this option?

If I program the dealer key first and it programs OK but the eBay key doesn't, should I just start a new session in diagbox and set it for 1 key and reprogram the dealer key?

[GiveMeABreak]

Like I said - the key will programme or it won't. Once the session is complete the dealer key should work fine, regardless of whether the cheap one does or doesn't. No need to do it again unless you obtain another key that needs programming.

[Ramc4]

Just out of interest, would a pro locksmith ever attempt to decrypt the security code from the eeprom by dumping the memory while out on a job?

Say a mobile locksmith was called out and the customer had lost their there but badly needed the car, you can decode and cut a key on the spot but can't program without the code but you can decrypt the code from a memory dump. So would this just be too unorthodox a thing to do on a callout?

[Paul-R]

If I understand correctly I believe that locksmiths go down a different route and clone a key rather than pair a new one in. How they do that if there's no key at all I don't know.