I cam across the this post on a website.. and posting here as is.
Each alarm has a unique 16 digit Hex code which should come on a RED plastic key card, about the shape of a credit card, and in my case was kept in one of the credit card slots on the left of my owners manual.
This number relates to both the original two fobs that came with the cars, and the alarm in the car.
Any new fobs, and I'm guessing here also if you wanted to reprogram an old fob for a different car, will need to have that 16 digit Hex code, or the alarm will not accept them in any way (so buying one from a scrap yard will need to be reprogrammed)
The alarm also has 7 'slots' where it can allocate associations with remote fobs.
By default slots 1 and 2 are allocated to the two fobs shipped when new, and any subsequent remotes will need to be allocated in one of the remaining 5 slots to ensure they work.
You can see this on the default RED plastic alarm card where it says under the 16 digit Hex code, in my case:
1* 2* 3_ 4_ 5_ 6_ 7_
When ordering an extra fob, it will need to be allocated to a 'slot' and in my case came with a second red key card which had on it:
1_ 2_ 3_ 4* 5_ 6_ 7_
to indicate that the new fob would go into 'slot' 4.
I spoke to Carl Baker and he was very helpful, however as I couldn't physically get to his location to reprogram my alarm (his preferred method of get everything is sync) I ordered an extra fob from Sam @ Abacus Alarms (
www.abacusalarms.co.uk).
They recommended a Meta TXM550 (
http://abacuscaralarms.co.uk/alarmshop/index.php?act=viewProd&productId=97) as the M100 (the one we all got with our cars) is no longer made.
As DaveD mentions you have to give them your 16 digit Hex code and then they can program a new fob for you.
Maybe we should make this a sticky post so that it can always be found?
Hope this helps clarify :-)
Alex