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View Full Version : Key stopped working - fob still works - how to fix key?


aussieallroad01
12-23-2013, 02:56 PM
I'm a newbie to the audiworld so please forgive me if I'm asking something pretty common.

I got two keys when I bought the car. One had no battery in the fob, and the other had a working fob with a battery that was running low.

I used the key with the working fob for some time, but yesterday I went to replace the battery and sort of bricked the car (or so it seemed). After replacing the battery, the remote fob still worked but the car refused to start and stay running using the key. The dash would show some flashing key light related to the immobiliser.

I searched a bunch of audi forums and found stuff related to the fob but nothing that got my key working:
http://forums.audiworld.com/showthread.php?t=2831663
http://forums.audiworld.com/showthread.php?t=2752117
http://forums.audiworld.com/showthread.php?t=1653558
http://forums.audiworld.com/showthread.php?t=2854254
http://forums.audiworld.com/showthread.php?t=1675022
http://forums.audiworld.com/showthread.php?t=1954050

After trying all that, the remote still works but the key still doesnt.

I've then tried the spare key with no battery, and found that it starts the car which I thought was bizarre. I dont have any battery for that one yet so the remote isnt usable.

Is there any way to restore my main key so that it will actually start the car?

Its kind of infuriating that someone designed something so silly that you can brick the key but not the remote by changing a battery.
OGBULLYLOCDAWG
12-23-2013, 03:36 PM
When you separated the key in half to swap the battery, by any chance did the transponder chip for the immobilizer fall out?

It's located on the key half portion and typically glue down:
http://i69.photobucket.com/albums/i44/derleicaman/B7%20Key%20Fob/B7KeyFob003.jpg
(photo by derleicaman)

Take the key apart again and see if the chip is still in there, or if it's damaged at all. If everything looks good and you didn't do anything else, like wrapping it in carbon fiber wrap. Maybe the chip failed?(don't even know if that's possible).

You can either take the good battery out of the key that's not working and put it in the one that needs it, or just swap over the key half to the already working remote.
aussieallroad01
12-23-2013, 03:44 PM
Oddly enough I did manage to drop the key but cant see the photo to see if what you're referring to went astray.

Didnt do anything else other than change the battery.

For some reason the two fobs have different sized batteries so I cant do that, plus im really looking to have both key pairs working (one for each driver)
OGBULLYLOCDAWG
12-23-2013, 03:52 PM
Oddly enough I did manage to drop the key but cant see the photo to see if what you're referring to went astray.

Didnt do anything else other than change the battery.

For some reason the two fobs have different sized batteries so I cant do that, plus im really looking to have both key pairs working (one for each driver)

http://i42.tinypic.com/2ef3lag.jpg

Does that show up for you?
aussieallroad01
12-23-2013, 04:24 PM
That has worked.

Is it the little brown/black rod that youre referring to? I dont recall seeing it - maybe it went astray when I dropped it. I will check and update.
rollerton
12-23-2013, 04:28 PM
There are a couple different fobs that works with the C5, but before you get confused- the "fob" and the battery have nothing to do with the Immobilizer. So, lets stick with one issue.
If you dropped the flip-key part of the remote there there's a chance you damaged the RFID chip inside. It's not common, those chips are very durable, but it is possible.
And really, without getting terribly technical if you have made no changes to the key / ignition assembly or done any software tweaking and still have one key that doesn't work and one key that does then you will at least need to have someone attempt to match the keys again.
BOTH KEYS.
Any time the Immo system is changed/ modified/ keys added then ALL KEYS YOU WANT TO HAVE WORKING must be re-paired at one time.
I Haven't ever had a key quit spotaneously, but I have bought a car that came with original keys that didn't work. I could verify that the key was matched to the car, but they would not start the car.
Doing the re-pairing procedure with VCDS and the Immo SKC worked~ so I've deduced that at some time the keys did work and quit working for some reason.
Other questions you migth ask:
1. Can you buy a used key and match it? ~NO. In Immo III the RFID chip becomes "bit-locked" to the Immo ID of a particular chassis.
2. How do I get the SKC? ~ A cheap Ebay "vag com" / KKL cable and vag commander will do it on the C5.
3. Will Vag Com get the SKC? ~NO. It will not.
4. How do I match the Immo and key after I have the SKC? ~You'll need a licensed Vag Com interface and they have a procedure on their website.
OGBULLYLOCDAWG
12-23-2013, 06:22 PM
That has worked.

Is it the little brown/black rod that youre referring to? I dont recall seeing it - maybe it went astray when I dropped it. I will check and update.

Yeah, it's the little glass pill that the pick is on.
aussieallroad01
12-23-2013, 09:45 PM
OGBULLYLOCDAWG - looks like you had it - the little glass capsule had fallen on the floor during the battery change.

All good now - thanks!

Have a merry Christmas!
OGBULLYLOCDAWG
12-24-2013, 12:08 AM
OGBULLYLOCDAWG - looks like you had it - the little glass capsule had fallen on the floor during the battery change.

All good now - thanks!

Have a merry Christmas!

Great to hear, glad you got it sorted out.

Happy Holidays!