Only key lost! Can this be replaced DIY using Diagbox?

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TawhidAhmed
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Only key lost! Can this be replaced DIY using Diagbox?

Post by TawhidAhmed »

Hi All,

I have lost my only key to my 2008 C4 Grand Picasso, and it was a 3 button flip fob.

I recently purchased a Diagbox package from EasyDiagnostics, and so I am keen to do as much of this as possible as a replacement key + programming looks to be over £200 in my area!

I want to clarify what I can do whilst spending the minimum amount of money possible, especially as I am in the middle of bringing it back to a roadworthy condition, not the best timing eh?
  • It looks like I can get mechanical and programming key codes from a Peugeot/Citroen dealership, and ask a locksmith to cut a blank key for me when I provide the mechanical key code.

    I can then use this cut key to unlock the car and program this new key to the car using Diagbox. In this process, will the alarm constantly go off?
I also have all of the neccesary information to provide to a dealership when asking for these codes- but no 4 character key code which I am happy to pay for.

Please correct me wherever I have got the wrong idea.

Thanks!
wheeler
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Re: Only key lost! Can this be replaced DIY using Diagbox?

Post by wheeler »

TawhidAhmed wrote:
18 Jun 2022, 14:33
  • It looks like I can get mechanical and programming key codes from a Peugeot/Citroen dealership, and ask a locksmith to cut a blank key for me when I provide the mechanical key code.
Yes a decent locksmith should be able to cut a replacement key from code, remember though Citroen will provide the mechanical key code it had when it left the factory, if the locks have ever been changed outside the dealer network the code may be useless, just something to bear in mind. Im not sure if your planning to supply your own key for a locksmith to cut, just be aware that many can be reluctant to cut keys supplied from unknown sources, the cutting buts on the machines can be expensive & they dont want to damage them.
You can also order a pre cut key from Citroen too, again if the locks havent been changed. Very expensive thought, around £170
TawhidAhmed wrote:
18 Jun 2022, 14:33
I can then use this cut key to unlock the car and program this new key to the car using Diagbox. In this process, will the alarm constantly go off?
Yes, if the car has an alarm it will go off when you open the car but wont stop the key from being programmed.
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GiveMeABreak
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Re: Only key lost! Can this be replaced DIY using Diagbox?

Post by GiveMeABreak »

If programming the fob(s) yourself (and you must programme all fobs you are going to use in the same session) you will need the confidential customer code. Citroen will provide this for a fee (anything from free to £20 ish). For that you can ask for the key codes and the confidential codes upon proof of ownership, and identification and a utility bill or similar.

The process within Diagbox is guided.

Yes you will have a problem with the alarm as without a key or fob with the immobiliser chip programmed it will prevent the car from starting and the alarm will sound. If you lock the vehicle with the mechanical key, it won't arm the alarm.

Edit: Post crossed over with Wheeler. ^
TawhidAhmed
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Re: Only key lost! Can this be replaced DIY using Diagbox?

Post by TawhidAhmed »

Thanks guys! Very useful! :) :) :)

I've been looking around online and a new programmed and cut key will cost in excess of £200, crazy :shock: . So i'm keen to do as much myself. Do you guys know how much a key will cost to be cut? Or supplied and cut by a locksmith?

I'm finding good blank programmable keys online for around £20, and I believe mine is a HU83 433MHz ASK, after seeing what pops up when I enter my reg at https://www.autowave.co.uk/catalogue/re ... ansponders

I understand that different frequencies are also available- how do I check which one is correct?

If it helps, my VIN is: VF7**************[VIN obfuscated, can be read by forum staff]
ozvtr
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Re: Only key lost! Can this be replaced DIY using Diagbox?

Post by ozvtr »

There are 3 parts to the key.
1) The blade. Every one knows how this works!
2) The transponder. This is an unpowered device that sends out a code that is relayed to the engine ECU on engine start up. It's about 1cm long and about 5mm wide. Some times they are in the key case or it might be on the transmitter PCB. Either way, it operates completely independent of the rest of the key, even if the fob battery is dead. If the transponder is "known" to the BSI it can be re-used during the key installation, otherwise it needs to be brand new. Used ones from another car will not work. They are known as an ID46 type transponder. The transceiver pickup coil (which picks up the transponder signal) is around the ignition switch. Again the transponder is only used to start the engine. Once the engine is running the transponder is not needed.
3) Central locking transmitter. This is the PCB that has the battery and buttons on it. It sends out a signal to the receiver located in the top of the COM's unit around the steering wheel (it has the switch stalks in it). The signal is de-coded and sent on to the BSI. The car locks/unlocks...or it doesn't. There are 2 types of signal modulation used, Amplitude Shift Keying (ASK) and Frequency Shift Keying (FSK). Which does your car use? Don't know! However the Chinese knock-off keys are cheap enough that you could buy one of each and try them. There is also an option in LEXIA in the BSI programing area for the "high frequency remote control transmitter type". It's a 4 digit alpha-numeric code. It's probably to tell the BSI what type of signal to expect from the key transmitter. Someone here might know what it means...I don't. If the central locking transmitter doesn't work, you could try different options in here. The two common frequencies used for central locking fobs is 315MHz and 433MHz. PSA seems to use 433MHz.

The transmitter and transponder are paired to the BSI and "locked" during the very first installation of a brand new key. Again, if the transmitter or transponder is already known to the BSI it can be re-coded to the car during the key coding phase. So only a brand new key or one known to the BSI can be "coded".
Can transponders be unlocked and re-used? Yes...BUT you need to know the locking code used to lock the chip in the first place! Most likely this is just a random number generated by the BSI to lock the chip. So, forget it. The transponder chips are very cheap anyway so why bother?
Can the transmitters be unlocked? Don't know. But I bet it's the same deal as the transponder chips.
The receiver module in the COM's unit is called the "high frequency unit" and it is also responsible for running the the transceiver pick up coil for the the transponder chip. If this stops working, neither the central locking or the engine will function!
If the BSI detects the central locking signal but doesn't recognize it, the BSI will not accept ANY signals for the next 60 seconds. This is to stop 'brute force attacks' on the central locking system.
The BSI and the transmitter code in the key are "synchronized" during a brand new key installation (and subsequently). However if the key fob is pressed more times than the signal is received (by the car), the BSI and the key will become de-synchronized and the central locking will not work. In this case you can re-synchronize them by inserting the key in the ignition, turn the ignition on and pressing either the lock or unlock button. Again, this only works for transmitters known to the BSI!
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Re: Only key lost! Can this be replaced DIY using Diagbox?

Post by wheeler »

TawhidAhmed wrote:
18 Jun 2022, 23:32

I understand that different frequencies are also available- how do I check which one is correct?
The frequency used depends on what part of the world the car is going to be used in, with just a few exceptions nearly all cars destined for Europe use 433 MHz. Some BMW models use 868 MHz. Asia & the Americas normally use 315 MHz.
As for the key blade type, the key number will give this away, HU83 blades have a key number starting either HCA or HOOH. If its a VA2 blade the key number will be made up of the letters A-F eg CDCABE.
For a start how much have the dealer quoted for both the codes? A decent locksmith wont need either of these as they will have the kit to get both the codes from the car.
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Re: Only key lost! Can this be replaced DIY using Diagbox?

Post by GiveMeABreak »

TawhidAhmed wrote:
18 Jun 2022, 23:32
I understand that different frequencies are also available- how do I check which one is correct?

If it helps, my VIN is: VF7**************[VIN obfuscated, can be read by forum staff]
Yours uses 433.92 MHZ HETERODYNE