What's the difference between a Q cccu and the AF cccu

Shell73

Shell73

A2OC Donor
Can anyone tell me what the differences are between the Q and AF cccu's because like an idiot I have just recieved an AF unit that I've bought from eBay when my unit is a Q unit. Guess I got excited by the £69.99 price tag. DOH!!!
My A2 is a 2001 1.4 petrol.

Thanks in advance.
 
I've got a fair understanding of the CCCU differences, though I've never compiled a table of my own. I once uploaded the same chart that can be found on the German club's wiki. See http://www.a2oc.net/forum/attachment.php?attachmentid=11229&d=1357312784
The table provides some information, but doesn't include information about which units only work with full electric glass rather than manual rear windows, which key fobs are cross-compatible, etc.

To answer the OP's question, the AF-unit can, in principle, be used to replace a Q-unit. The AF-unit is a later, more reliable unit that has all the same functionality as the Q-unit. However, key fobs that talk to a Q-unit will not talk to an AF-unit, meaning that alternate key fobs are needed should you wish to make the change.
My car was originally made with a Q-unit, but I changed it for an AF-unit when the opportunity arose, simply for its greater reliability. Fortunately for me, the AF-unit that I sourced came with two compatible key fobs.

For reference, the part number of the key fob that can be linked to an AF CCCU is 8Z0 837 231 D. The D on the end is essential.

Cheers,

Tom
 
Thanks guys for your replies. That will explain why I've lost the remote locking from my fob. Thanks again.
 
Shell73 said:
Thanks guys for your replies. That will explain why I've lost the remote locking from my fob. Thanks again.
Click to expand...
Hi
Even if you bought exactly the same model CCCU as yours, you would still lose the remote functionality until the keys are re-synched to the unit via VCDS.

But in this case you will need the fobs and someone who can synch them to your car (can't be done with VCDS because the immobiliser chips will need to be sorted)

Steve B
 
Birchall said:
Even if you bought exactly the same model CCCU as yours, you would still lose the remote functionality until the keys are re-synched to the unit via VCDS.

But in this case you will need the fobs and someone who can synch them to your car (can't be done with VCDS because the immobiliser chips will need to be sorted)
Click to expand...

Steve is right about the first point but not about the second.

Yes, even if you buy the appropriate fob for your AF-type CCCU, you'll need someone with VCDS software (like myself and plenty of other committed A2 nerds!) to match that fob with your CCCU. Clearly the correct fob on its own doesn't just work automatically, otherwise people could just buy fobs on eBay and walk around opening other people's cars! :p

The fobs themselves are split into two halves: the lower half with the buttons on it is responsible for talking to the CCCU and thus controlling the central locking. The upper half (with the metal flip-out blade) contains a chip that is matched to your car's immobiliser. When you insert your key into the ignition, the black plastic ring around the ignition barrel reads the chip in the upper half of the key and decides whether it's going to let you start the engine or not.
If you were to buy an appropriate fob for your AF-type CCCU, you'd need to combine the lower half of the purchased key with the upper half of your existing key. :)

Cheers,

Tom
 
Hi Tom
yes I forgot you could switch the key section to retain the existing chip.

Steve B
 
So do I need to be chasing the guy who I bought the cccu from to see if he has the key fobs ?
 
Shell73 said:
My heads ready to explode. Such a complex little car.
Click to expand...

If you have no joy, the next thing to do is look on eBay for the part number that I listed previously. I'd recommend searching both with and without the spaces.

It all seems quite baffling when it's new, but if you're at all technically minded, you'll get to grips with the A2's ways. :)

Cheers,

Tom
 
Okay everyone. My replacement key has arrived today. It is the correct part number . Do I now have to have this key reprogrammed to communicate with my CCCU ?
 
Shell73 said:
Okay everyone. My replacement key has arrived today. It is the correct part number . Do I now have to have this key reprogrammed to communicate with my CCCU ?
Click to expand...

Yes, you do. If there's nobody more local to you who can do it, I'm in Lancaster and am happy to help.

Cheers,

Tom
 
Timmus. Thank you very much . I really appreciate the help you've given to me so far. There's a guy in Barnsley who can do it who has VAGCOM equipment. He also did the fault finding a couple weeks ago. But thankyou again for your generous offer.
And if anyone needs a VAGCOM fault finder who's in the South Yorkshire area then I will gladly pass his number on .
 
Key had been programmed to the car and everything is back to normal and working perfectly. Thanks again Timmus and everyone else for their help and advice .
 
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