C3 Ignition Key Failure

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chazaiki
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C3 Ignition Key Failure

Post by chazaiki »

Hi Guys

one of my keys i kept in the glovebox decided it would only work the remote locking / unlocking but wont start the engine. Message displays Antitheft fault. I have tried the hold lock button in the ignition and disconnected car battery to see if anything resets but still the same.

car is citroen c3 2007 petrol and flip key

Any ideas why one key works and other has decided not to start engine but central locking buttons work fine, Cheers, Chaz
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Re: C3 Ignition Key Failure

Post by CitroJim »

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Re: C3 Ignition Key Failure

Post by addo »

It could be that the BSI has simply "forgotten" the second key. It occasionally happens, especially if there's been incidents like a dead flat battery.

Trying to re-program both keys using a Lexia is the simplest approach, you will need the secure code for this (four character code on a credit card sized plastic slip in your car's handbook paraphernalia).
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Re: C3 Ignition Key Failure

Post by Pug_XUD_KeenAmateur »

Been scouring the Archive Forums and Internet for Advice. Do the above posts apply similarly re the following?

Daughter came around with a new casing for her C3 Key and we decided that actually, the Spare Key was in better shape, the internal and external buttons to ‘Her’ key being mullah’d (I’ve always kept the Spare); so we re-cased that instead.

Both keys were working just fine, albeit without the convenience of the ‘Plip’ function.

Having fitted a replacement casing I thought to myself ‘Good practice to renew the Fob Battery while I’m at it, its at least two years old - the length of time she's had the car’. I did so, tried the key and found that only the ‘Lock’ Button would work… except it wasn’t working. The Central Locking made a suitable ‘Activate’ Noise upon depressing the relevant button lock, with an appropriate brief flash from the Indicators; but the result was actually an Unlocked car. I suspect the CL Motors were actually Locking and Immediately Unlocking.

So after a bit of scouring the Internet, I came across this
https://citroenc3owners.com/tips-for-an ... 3-t71.html

I followed the instructions and this improved matters; with both Lock and Unlock now working correctly and the actual Door Locks doing what they’re supposed to.

But still the Starter turns uselessly unless the other key is ‘within range’ to talk to the Immobiliser, which is actually quite generous, about 20metres or so.

There was an associated post linked from the above, but this spoke of a 4 Digit Code on a Card that I know she doesn’t have.

Is there anything more I can do to get the ‘new’ key to start the engine?

And anyone have any advice about key numbers or suchlike coz Daughter now requires both keys to use her car, and if she loses them she’s in deep doo-doo’s! With the cost of Main Dealer Keys believed to be in excess of £150, a lost key would amount to nearly half what she paid for the car!

The little voices in my head are fighting:
First one says
‘What was I thinking messing with a modern?!’
while second says ‘But You only Re-Cased a Key and changed a (Fob) Battery’
and the first responds ‘Yes but it’s a Modern, with associatedly baffling electronics, that’s enough!’

I did see another post suggested that disconnecting the Battery might do some good, but I’m very loathe after such a seemingly innocuous procedure has caused problems.

It’s a 2005 1.1 Petrol by the way.
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Re: C3 Ignition Key Failure

Post by Hell Razor5543 »

There is an immobiliser chip within the casing somewhere. With some (but not yours, it seems) it is on the main circuit board, while on others it is either in a separate cavity in the fob body, or in a small cavity in the key head (that pivots). Typically it looks like a large glass grain of rice.

The car, when the key is turned, looks for this chip (via an inductance coil) and reads the value. If the immobiliser electronics in the car recognise that chip they will allow the car to start, otherwise it is no-go.
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Re: C3 Ignition Key Failure

Post by GiveMeABreak »

The transponder does not work at a distance, so the fob being 10 meters away isn't relevant - that is only for the remote functions of locking and unlocking.

The fob has to be in the ignition to start the car.

Have you followed any of the resynchronisation procedures needed when replacing a battery or if the fob has not been used for sometime?

Assuming you have the transponder chip in both key fobs that should be all you need. However, a new fob will need to be coded to the vehicle and the 4 digit code is required in order to programme it. This is the Customer Confidential code. Citroen will supply it with evidence of ID, Address and vehicle ownership for a fee of anything from free to £25 depending on how well you know your dealer :-D

Once you have that you can programme your new key fob with Lexia. If you want the resynchronisation procedure, pop up the reg or the VIN of the C3 as it may be different depending on architecture.
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Re: C3 Ignition Key Failure

Post by Pug_XUD_KeenAmateur »

Thanks James, after rooting through the kitchen bin, it looks to me like its here (see pic). Unfortunately, it seems SWMBO had thrown away a load of Cocoa Powder.
EPSON003.JPG
I think the linked page procedure I found could probably be described as a re-synchronisation procedure, Marc and hopefully the visit to a Citroen Dealer won't be necessary....

...particularly if I can get hold of half a genuine Citroen key of that vintage.

I'm thinking that the way to go is to replace the 'Button' side of the key only, thus retaining the Transponder, but gaining working Plip Buttons.

Anyone got a similar vintage of PSA Key with good Buttons that they're happy to pass on for a few squid? Only the Button side required. (not the PCB, Chip or Key Shaft; but a complete one is fine too)
IMG_20190625_142937737.jpg
full.jpg
CE0365?

I know that half the new Fob is different enough by a 1mm or two that it won't fit the old key as we tried that pretty much straight away; daughter stating a preference to keep the original Citroen Logo.

Apologies that I've not had much to add to the Forum of late btw, but my 405 is getting rather neglected of late; its even overdue an oil change! (usually about 8k, currently about 12k). It is off to a show this coming Sun' though!
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