Spare key only "partly" coded?

[Matt UK]

Wifey has a 2005 VW (a Sharan if your interests include over-sized MPVs) and I had to use the spare key today - I think for the first time ever.

It let me manually unlock the car and get in - so far so good.
Then the alarm went off - damn, obviously the alarm has not turned itself off.
Stick the key in the ignition to let the car know I am not nicking it - alarm continues. Damn.
Start car up - turns over, then dies. Obviously an immobiliser still thinking I'm nicking it.
Hop out and lock it - alarm turns off.

Repeat from the start a couple of times - same result.

Whats going on - is the key only partly coded? How comes it recognises the key to let me unlock and then we get no further? Can I solve this myself doing a sequence thing, or do I need a pro to bill me the appropriate hourly rate?

[Remagel2507]

If it doesn't start the car then you will need someone to code it using the appropriate software, although you can use a standard VAG COM program to code the key you may need a specialist to read the immobiliser code from the car first

[ajondyh]

The remote and the immobilizer are 2 different systems in the key and on the car. The remote buttons open the door and switch off the alarm but there is a separate transponder in the key which disarms the immobilizer. (Most VAG cars will start for a second or so with a non programmed key) It seems that someone has programmed the existing (Working) key whilst your spare was not present. This has the effect of deleting the non present key as all keys need programming at the same time. This is not the case with the remotes which need to be physically deleted diagnostically otherwise they remain programmed.

HTH
Andy

PS: Go to www.autolocksmiths.net to find your nearest capable auto locksmith

Edited by ajondyh on Monday 6th January 23:35