Is the tag code you're referring to the one inside the key on the electronics? You should be able to pull out the "guts" and fine an 8 digit number in there--you can use that to program the unlock/lock functions to your car on your own. You'll have to get the dealer to do the immobilizer work, but they should be able to reprogram the immobilizer you already have.
How to program the electronics:
Programming the remote transmitter code (from the owners manual)
read through this first since eveything needs to be done in a quick sequence
1. Sit in the driver's seat, close all doors and the rear gate or trunk lid etc
2. Open and close the driver's door one time.
then Within 45 seconds
3. open and close the driver's door once
4. turn the ignition key from LOCK to ON 10 times within 15 seconds.
An electronic tone will sound once, a buzzer will continue to sound and the interior light will continue to flash until the transmitter codes are completely registered.
If you do not perform the steps above within 45 seconds an error will occur and neither an electronic tone nor the buzzer will sound and the interior lamp will not flash. In this event, start all over again.
Within 45 seconds do the following
Open and close the driver's door once within 15 seconds and an electronic tone will sound for 30 seconds. If you do not perform the operations within 15 seconds an error will occur and the electronic tone will not sound. In this event, perform the registration steps again beginning with # 3 above.
Ok, here is the fun part...
Before the electronic tone stops, press the power door lock button to LOCK the same number of times as the leftmost digit of the transmitter code.
For example, press the LOCK button 8 times if the leftmost digit of the code is 8. If the number is 3 then LOCK the door 3 times etc...
When you have finished entering the number, push to UNLOCK side within five seconds and
Then do that for all the remaining 7 digits of the code. After each series pull the lock knob to the UNLOCK side within five seconds.
When you are finished, within 5 seconds push that LOCK button to UNLOCK one time and then do it all again, the full series.
Yes, once again start with the left digit and re-enter each one using the lock button within a few seconds.
When you have entered the eighth digit the second time an electronic tone will sound for 30 seconds.
The electronic tone will stop sounding when you start entering the number. If you do not start entering the number using the lock knob before the electronic tone stops sounding, an error will occur. In this event, perform the registration steps again beginning with part 3 above.
If the interval between one push of the knob and the next exceeds five seconds, an error will occur.
In this event, perform the procedure again beginning with part 4. If an error occurs six times, perform the procedure again starting with part 3.
If the code entered the second time is not identical to the code entered the first time, an error will occur. In this event, perform the procedure again beginning with part 5. If an error occurs five times, perform the procedure again starting with part 3.
If you wish to program another transmitter code into the system (up to four transmitter codes can be programmed into the system), perform the procedure beginning with part 4. When you have finished programming all of the necessary transmitter codes into the system, remove the key from the ignition switch.
Test to make sure it's right
Deleting old transmitter codes
The control unit of the keyless entry system can store 4 transmitter codes.
Lost transmitter the lost transmitter's code remains in memory. For security reasons, lost transmitter codes should be deleted from the memory.
To delete old transmitter codes, program four transmitter codes into the system. If you have only one current transmitter, program it four times. If you have two
current transmitters, program each one twice. If you have three current transmitters, program two of them once and the third one twice.
This process will leave only current transmitter codes in the system's memory.
Make sure no one else is operating their keyless entry system within range of your vehicle when programming transmitters. If someone else were to operate their remote transmitter while you are programming your transmitters, it is possible that their transmitter code will be programmed into your system, allowing them unauthorized access to your vehicle.
or just call your local dealer!