C5 Program Spare Key With Lexia

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Paul-R
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Post by Paul-R »

acrowot wrote:Paul what is the problem that you have, it seems that you have tried to do what I am trying to do but without success.
I'm not sure.

Maybe the locksmith who cut my blade is right, there is more than one type of fob, which looks the same but is different. I do doubt it though.

More likely is that the fob I picked up from a (French) scrappy is invisibly damaged in the solid plastic part of the fob where the blade goes in.

This post has made me guilty that I just let this slide. I'll dig out my collection of scrappy fobs and start again.

Not this weekend though. Dad's taxi is taking daughter back to uni!
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Post by acrowot »

This Keyfob I have was working when I bought it, I started the car that it was in with it. It was a C5 but with a petrol engine in it, it looks the same as the one I have for my car but who knows.
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Post by Paul-R »

You have the advantage that you've seen it working - mine was from a scrapper.

Best of luck!
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Inside every old person is a young person wondering what the hell happened.

"Trying is the first step towards failure" ~ Homer J Simpson​
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Post by wheeler »

MikeT wrote:No, the ECU (which can hold at least three key codes that I know of) is first wiped of all programmed keys when you program new ones. You could program my key to start your car (if the key fitted the ignition) as I could program yours to start mine.
Have you actually tried that ? I believe the transponder chip in the key can only be written to once, They can be re synced to the same car again but i dont think they can be programmed to a different car.
You can have upto 5 keys programmed to the one car.
Im also not sure if i understand what has been said about the security codes & ECU's But the BSI & injection ECU have the code from the security card sored in them, they can both only store one code & the code can never be changed once it has been programed into the ECU & BSI. Both these codes must be the same or the car will not start.
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Post by acrowot »

wheeler wrote:
MikeT wrote:No, the ECU (which can hold at least three key codes that I know of) is first wiped of all programmed keys when you program new ones. You could program my key to start your car (if the key fitted the ignition) as I could program yours to start mine.
Have you actually tried that ? I believe the transponder chip in the key can only be written to once, They can be re synced to the same car again but i dont think they can be programmed to a different car.
You can have upto 5 keys programmed to the one car.
Im also not sure if i understand what has been said about the security codes & ECU's But the BSI & injection ECU have the code from the security card sored in them, they can both only store one code & the code can never be changed once it has been programed into the ECU & BSI. Both these codes must be the same or the car will not start.
This would support my local locksmith who says the keyfob can only be programmed once, but it is being suggested here that it is not the keyfob that is programmed with Lexia, rather the ECU is programmed with up to 5 different key codes. I have read into what is being said that the keycode on the credit card is not the same as the code stored in the keyfob rather it is an enabler for the ECU to be programmed with the codes in the fobs.
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Post by Paul-R »

acrowot wrote:This would support my local locksmith who says the keyfob can only be programmed once, but it is being suggested here that it is not the keyfob that is programmed with Lexia, rather the ECU is programmed with up to 5 different key codes.
That's my understanding as well. I thought that that each fob transponder has a unique code which is programmed at the factory and which is then synced to the ECU using a Lexia.
acrowot wrote:I have read into what is being said that the keycode on the credit card is not the same as the code stored in the keyfob rather it is an enabler for the ECU to be programmed with the codes in the fobs.
That's a good analogy I think. You also need this code to have a blade cut by a keysmith.

Just for your information This thread has my description of the physical process to change the blade.

http://www.frenchcarforum.co.uk/forum/v ... sc&start=0

I really, REALLY must get my collection of scrappy fobs out (another 2 I think) and work my way through them.
As I get older I think a lot about the hereafter - I go into a room and then wonder what I'm here after.

Inside every old person is a young person wondering what the hell happened.

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Post by MikeT »

wheeler wrote:
MikeT wrote:No, the ECU (which can hold at least three key codes that I know of) is first wiped of all programmed keys when you program new ones. You could program my key to start your car (if the key fitted the ignition) as I could program yours to start mine.
Have you actually tried that ? I believe the transponder chip in the key can only be written to once, They can be re synced to the same car again but i dont think they can be programmed to a different car.
No I haven't tried it but would be willing to test my theory on my car, I'm that confident. I was basing this on my understanding of how passive RFID technology works in reference to my Xantia. I don't know if the C5's use a different system so I apologise for not making this clear.
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Post by wheeler »

Paul-R wrote: You also need this code to have a blade cut by a keysmith.
The mechanical keycode for cutting new keys is totally different to the 4 digit confidential code on the plastic card. The mechanical code is 10 digits long, the first 3 digitd identify the blank & the last 7 are the cuts. It comes with the new car on the keytag on a pice of paper with a barcode on it.
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Post by acrowot »

The keyfob I have now has a key blade in it that was cut by my local locksmith, I followed Paul-r's post to fit this keyblade into my fob. The locksmith did not have a barcode or anything else off me as I did not have it, I presented him with the fob and broken blade and he had a machine ( he said it cost a few grand ) and I believe this machine scanned the contour of the 2 pieces and he produced a key from it which is a spot on fit. The key that he produced would only of course unlock the door it would not start the car, it cost £14.00 it is now in my original fob and does all that the original did.
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Post by wheeler »

You would only need the mechanical keycode if you dont have a key to copy from. Some machines can cut a new key just from punching in the code.
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Post by acrowot »

wheeler wrote:
Paul-R wrote: You also need this code to have a blade cut by a keysmith.
The mechanical keycode for cutting new keys is totally different to the 4 digit confidential code on the plastic card. The mechanical code is 10 digits long, the first 3 digitd identify the blank & the last 7 are the cuts. It comes with the new car on the keytag on a pice of paper with a barcode on it.
Wheeler thanks for your help so far, on the back of my credit card lookalike is a barcode and under the barcode there are 12 digits in this format, these are not the actual numbers:-A800000088CN the last 4 digits are the transponder code would you know what the previous 8 represent, would these letters and numbers relate to the mechanical keycode, is it likely that the last 4 letters and numbers are what is actually under the security label on the front of the card, I do not want to remove it,it does seem a little pointless having these numbers under cover on the front and displayed on the back.
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Post by Paul-R »

wheeler wrote:The mechanical keycode for cutting new keys is totally different to the 4 digit confidential code on the plastic card. The mechanical code is 10 digits long, the first 3 digitd identify the blank & the last 7 are the cuts. It comes with the new car on the keytag on a pice of paper with a barcode on it.
Ah, I just passed over the piece of paper with all the code information to the locksmith. My mistake.
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Inside every old person is a young person wondering what the hell happened.

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Post by wheeler »

acrowot wrote: Wheeler thanks for your help so far, on the back of my credit card lookalike is a barcode and under the barcode there are 12 digits in this format, these are not the actual numbers:-A800000088CN the last 4 digits are the transponder code would you know what the previous 8 represent, would these letters and numbers relate to the mechanical keycode, is it likely that the last 4 letters and numbers are what is actually under the security label on the front of the card, I do not want to remove it,it does seem a little pointless having these numbers under cover on the front and displayed on the back.
The last 4 digits on the back are whats under the scratch off panel & yes it is kind of pointless to have the 'secret' code printed on the back. I have no idea what the digits before it represent but it's definitely not the mechanical keycode.
The mechanical code will be on a seperate slip of paper with a barcode on it & the code will be in the format SF1 0612468. I shoud have said the keycode may be 9 or 10 digits long depending on the type of blank. The last 7 digits will always be numbers, The first 3 (or2) digits can be a mix of letters & numbers.
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Post by JohnD »

Let me throw in my two penny worth on this. My C5 came with three keys; two plips and a key which would only unlock the doors (and sound the alarm) I had one plip stolen so I bought another off ebay.

I got a single key cut on the high street, copied from my own. Next I bought a plip off ebay. By putting the ebay key in a vice I was able to knock the plastic away from the blade. No rivets to drill; it just knocked straight off. Next I cut away all the plastic off the high street copy then made both blades the same length. The high street blade pushed into the ebay plip and was held firmly.

Then I took both plips and the 'credit' card with the code to my local Cit dealer and asked them to programme the new plip to the car. After 24 hours they said it couldn't be done. I then called a mobile auto-locksmith who came to my home. At first he had no success then he replaced the chip in the base of the ebay key. Finally he left me with the ebay plip which would manually unlock the car and start the engine but wouldn't work the central locking.
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Post by Paul-R »

JohnD wrote:By putting the ebay key in a vice I was able to knock the plastic away from the blade. No rivets to drill; it just knocked straight off.
Yes, I could have done that but TBH it's a bit brutal and it didn't take very long to drill the two bits of plastic out and then work the blade out by hand.
JohnD wrote:Next I cut away all the plastic off the high street copy then made both blades the same length. The high street blade pushed into the ebay plip and was held firmly.
Mine was not so firm so I filed the two little cutouts to match the original and the positioning of the holes in the fob.
JohnD wrote:At first he had no success then he replaced the chip in the base of the ebay key.
What exactly do you mean by that? I'm very curious.
JohnD wrote: Finally he left me with the ebay plip which would manually unlock the car and start the engine but wouldn't work the central locking.
This is two separate things. He has synched the car with the transponder in the plastic head which the blade is pushed into but the remote locking transmitter in the swivel part isn't working.

Did he check to see if it was transmitting or not? Have you tried to pair the locking/unlocking bit yourself? It's very simple; put the key in the column lock, turn to the ignition position (not start) and press one of the lock/unlock buttons. Keep the button pressed for several 10s of seconds, then take it out and try the lock button
As I get older I think a lot about the hereafter - I go into a room and then wonder what I'm here after.

Inside every old person is a young person wondering what the hell happened.

"Trying is the first step towards failure" ~ Homer J Simpson​
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