2008 xc90 transponder/remote code concepts

[ogatrulle]

Like many of you, I will be obtaining additional keys/fobs for my xc90. Can someone please clarify some details about transponder and remote programming? I have read what I could find online but still don't fully understand. Many thanks for ensuing enlightenment.

First, here is my current understanding (please correct me if this is erroneous):

1. The factory-supplied xc90 keys contain two independent electronic elements: a) a small glass capsule with an RFID chip ("transponder"); and b) an RF remote with buttons for door lock/unlock, etc. ("remote" or "fob").

2. The transponder contains a unique numeric code in its memory and can receive and send small messages over small distances (a few cm) via RFID.

3. Via an antenna in the steering wheel around the keyhole, a computer in the car communicates with the transponder if it is close to the steering wheel. The car computer keeps a list of allowed transponders. If the transponder in the key is on the list, the computer allows the car to start if the car computer can communicate with the transponder.

4. The remote/fob also has an identity code which is transmitted as part of the message when a fob button is pressed.

5. The car computer also maintains a list of allowed fob identities. If the car receives a fob message with a code on its list, the computer allows the door to unlock or whatever.

My questions have to do with how the programming process works:

1. I have seen discussion of a programming code that the seller of the key/fob must provide. Does this code apply to the transponder or to the fob?

2. On a related note, I understand that the code is provided to Volvo/VIDA and that some computed result is then loaded into the car computer. Does that download apply to the transponder or to the fob?

3. Maybe either the car computer's transponder list or fob list is set MERELY according to the presence of the transponders or fobs when VIDA is told to match them to the car. If so, which?

4. I have read that codes in the transponder chips themselves can sometimes be modified (through RFID commands). Does the normal Volvo programming process modify the transponders at all?

[doublebug]

Understanding is correct.

Questions:
1 fob
2 fob
3 both
4 Yes

[ogatrulle]

doublebug, thank you for your answers. May I ask for further clarification:

3. Maybe either the car computer's transponder list or fob list is set MERELY according to the presence of the transponders or fobs when VIDA is told to match them to the car. If so, which?

3 both

I am confused. Since making the fob valid for the car requires the fob code, it seems that presence of the fob at programming time is not sufficient. Do you mean that it is required?

[yagger]

The chip immo is programmed via the antenna in the ignition lock, therefore you need to keep key in the ignition when programming immo. To program the remote control you only need to program the codes into the car. To program the remote do not need to keep it in the car.

[ogatrulle]

Thank you, I understand. (and I believe immo = transponder)

[doublebug]

yes

[xyourobob]

I bought new fobs off Ebay, I used a dremmel to cut out the old transponder (just take your time) and it was very easy to install into the new fob. Use some type of glue to hold fob half's together or they will come apart when you turn key in the ignition. Two new key fobs for less than $20.00