C4 Replacement Fob Not Working

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Re: C4 Replacement Fob Not Working

Post by GiveMeABreak »

That should just mean you have a physical key to start the car - as opposed to keyless enty and starting. Remember these BSIs are shared across different vehicles not just for the C4 :wink:
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Re: C4 Replacement Fob Not Working

Post by Cutac »

:(

That's it, I can't think of anything else :mrgreen:
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Re: C4 Replacement Fob Not Working

Post by GiveMeABreak »

Bite the bullet and get one from your dealer as you suggested - the price should include coding it to the vehicle for you (they never charged extra to do this in the past with me).
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Re: C4 Replacement Fob Not Working

Post by Cutac »

But the best part is that if it doesn't work, I'll be refunded or it will be made to work!
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Re: C4 Replacement Fob Not Working

Post by GiveMeABreak »

Well the answer to that is:

If you go in and say I want a new key fob, they'll first ask you if you want one with or without a cut key and order it. Once it is in and they code it great. If it won't work after coding, they will check to see if there is a fault with the car and if so, they will advise you of the recommended repair. So as these are special order, they won't refund you if there is another fault on the car that is preventing the receipt and sending of transmissions.

As the fob will be original and brand new including a new battery - the only other likely possibility is the Control module under the steering wheel that acts as the transmission receiver from the fob that talks to the BSI to allow the doors to be unlocked. This unit also controls the lights, wipers etc., so if it is faulty it may be not accepting the signal. So as Paul said earlier - if you know the unit is sending the signal - and is sending the correct code, then wither the control module under the steering wheel is faulty or the communication between this unit and the BSI.
Cutac Comms Unit.PNG
(No 1) Switching Block Remote Control (Comms Unit)
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Re: C4 Replacement Fob Not Working

Post by xantia_v6 »

Be aware that if they order a key by VIN, you might get a 2 button key, if that is what the computer says!
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Re: C4 Replacement Fob Not Working

Post by GiveMeABreak »

Guaranteed - as they don't list a 3 button one under this VIN
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Re: C4 Replacement Fob Not Working

Post by Cutac »

Sheesh, thanks Xantia!
I'll go and try and order a 3 button fob, if there'll be a guy who I'm good with, I don't think he'll refuse to order it.
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Re: C4 Replacement Fob Not Working

Post by Cutac »

Being a stubborn type, I'll order another cheap key from aliexpress. This time, I'll buy an old style 3 button key.
I've got 2 questions. First, ASK or FSK, what's the difference? And second, why doesn't any Aliexpress key have one microchip that original 3 button keys(VTS) have? What's that microchip for?
Chip is in the circle.
Image

Also, can an old style key provide remote window closing and opening(car supports it) on a second gen c4?
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Re: C4 Replacement Fob Not Working

Post by GiveMeABreak »

They are both digital forms of modulation techniques, each carries the signal in a different way - have a Google for the science bit :-D
Amplified Shift Keying
Frequency Shift Keying

In the Fob and the key without a fob, you'll have the transponder chip that is picked up by the aerial in the ignition barrel area.

The fobs have additional circuitry to activate the remote locking and unlocking, so need to send a rolling code between the fob and the BSI (encrypted) so that they can handshake and unlock the car. It will also send certain codes to unlock the boot or guide me home lights or the tailgate release & opening (X7) / window lowering / closing etc. depending on model and programming of the BSI and other ECUs.

As for Ali X - best ask them! :-D
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Re: C4 Replacement Fob Not Working

Post by Cutac »

I did some Googling and let's say I get the differences, but which one should I pick for B7 c4? FSK seems "better", but I've not encountered any article regarding PSA cars.
GiveMeABreak wrote: 03 Sep 2018, 20:24 The fobs have additional circuitry to activate the remote locking and unlocking, so need to send a rolling code between the fob and the BSI (encrypted) so that they can handshake and unlock the car. It will also send certain codes to unlock the boot or guide me home lights or the tailgate release & opening (X7) / window lowering / closing etc. depending on model and programming of the BSI and other ECUs.


What did you want to say by this? :)
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Re: C4 Replacement Fob Not Working

Post by Cutac »

Also, one more thing. 0523 and 0536 mean just that battery sockets are different or something else is, too?
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Re: C4 Replacement Fob Not Working

Post by GiveMeABreak »

Cutac wrote: 03 Sep 2018, 23:04
I did some Googling and let's say I get the differences, but which one should I pick for B7 c4? FSK seems "better", but I've not encountered any article regarding PSA cars.
It's not a matter of picking one - you need one that is the same as the original or it won't decode the signal. Which one it is I can't say - another reason to get a proper one from the dealer, unless you want to keep trying them out and sending them back.
GiveMeABreak wrote: 03 Sep 2018, 20:24 The fobs have additional circuitry to activate the remote locking and unlocking, so need to send a rolling code between the fob and the BSI (encrypted) so that they can handshake and unlock the car. It will also send certain codes to unlock the boot or guide me home lights or the tailgate release & opening (X7) / window lowering / closing etc. depending on model and programming of the BSI and other ECUs.

What did you want to say by this? :)
Because you asked what the circuitry was for.
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Re: C4 Replacement Fob Not Working

Post by Cutac »

Yeah, but those chinese keys seem to be working without that one chip I've circled.
I wonder what it is supposed to do, i.e. what that key can't do since that chip is missing.
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Re: C4 Replacement Fob Not Working

Post by Cutac »

And on 0536 keys, chip is present.
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