C4 Replacement Fob Not Working

[Cutac]

Bought a new 3 button key for 2011 c4 from aliexpress and it doesn't work. It's been cut and synchronized to the BSI(car starts with it), but remote functions don't work. Battery is new. Any ideas?

[EDC5]

Is the key the same frequency? There are 433MHz and 434MHz types depending on age.

Have you attempted to synchronise the remote function?

[Cutac]

According to the aliexpress listing, it's a 434Mhz model.
I did try to synchronise, using various methods, but neither of them worked.

[Cutac]

And according to my VIN on service.citroen:
LOCKING REMOTE CONTROL FREQUENCY 433.92 MHZ HETERODYNE
But on the plaque I recieved with my car keys(when I bought the car), it says 433Mhz key made by Delphi.

Can that be changed in Diagbox maybe?

[GiveMeABreak]

Because it probably isn’t compatible with the earlier system in your C4. The circuitry and software have to be compatible with the car’s architecture. It’s like trying to use tech from a 1995 chip to work with a car today, only in reverse.

[Cutac]

But it's weird since I've got the same 3 button key and it works from the factory.
I've checked few cars on service(2011, 2013 and 2014, which is exclusive) and all have that same 433.92 Mhz frequency. So how come are my factory keys 433 MHz?

[GiveMeABreak]

Ok 2 separate things going on here. There is the transponder chip for the starting of the car. Then there is the remote locking and unlocking using the fob and optionally a middle button for lights or boot opening etc.

So although the transponder chip has been coded and paired successfully, the other electronics for the remote function may not.

[Cutac]

Yeah, I know that, but I have a three button key from the factory and it works, but the exact same one from aliexpress doesn't.
If my car has 434MHz reciever, how does the factory 433 MHz key work?

[GiveMeABreak]

But are you understanding? The MHz is just the frequency the remote is operating on. If it is not sending the right information it won’t make any difference, i.e. it may be sending garbage if the BSI us not understanding the message, regardless if the frequency!

Let’s clarify something first. When you paired the new key with Lexia. Did you pair ALL the keys together in the same session?

If you did this then your Ali key is probably not compatible.

[GiveMeABreak]

If the fob from 'Ali Exp' is designed for the later model C4 (from 2011 on) it just won't be compatible with your earlier C4 (2006). The models are completely different and that may be a different electronic architecture for the remote operation / different BSI so won't be able to understand the locking / unlocking requests.

The immobiliser code / circuitry is different to the remote locking and unlocking / button function circuitry.

It's like your C4 speaks Russian, the old fob speaks Russian, but your new fob is speaking German - it doesn't understand the remote locking / unlocking / button functions.

[Cutac]

If the fob from 'Ali Exp' is designed for the later model C4 (from 2011 on) it just won't be compatible with your earlier C4 (2006). The models are completely different and that may be a different electronic architecture for the remote operation / different BSI so won't be able to understand the locking / unlocking requests.

The immobiliser code / circuitry is different to the remote locking and unlocking / button function circuitry.

It's like your C4 speaks Russian, the old fob speaks Russian, but your new fob is speaking German - it doesn't understand the remote locking / unlocking / button functions.

No, no, it is a newer model C4. VTS is a different car, this one is B7 C4 from December of 2011.

Let’s clarify something first. When you paired the new key with Lexia. Did you pair ALL the keys together in the same session?

If you did this then your Ali key is probably not compatible.

Yes I did, I've paired them at the same time. I'll look into the Diagbox today to see if there are any options regarding keys. I'll also try pairing them again.

[GiveMeABreak]

Ok, maybe time to update your profile with the other car too What's your VIN for the newer one then - I'll see what I have...

But there aren't any other options apart from pairing the keys. Only 2 procedures to follow - Pairing the transponders with Diagbox and re-synchronising that doesn't need Diagbox.

[Cutac]

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

I'll update my profile after I post this

As you said, I've paired transponders which is a one time deal. But as for re-sync, what methods should I try? I did what Diagbox told me, ignition on, hold button for 5 seconds, ignition off; did what manual said, and did something I've found online, ignition on, hold for 30 seconds, ignition off. And neither worked.

[GiveMeABreak]

Right - so you've got the wrong one then. The one specified for your car's VIN is a 2 button one. Your model isn't compatible with the 3 button fob electronics.

6490FS (uncut)
6490FT (Cut)

[Paul-R]

Was this new key & fob an extra one or to replace a previous (broken) one?

My thought is that if it's to replace then you might be able to take the fob electronics out. This would only be possible if the immobiliser chip is separate to the lock/unlock circuitry though.

EDIT

Overtaken by events!