GM Service Manual Online
For 1990-2009 cars only
  1. Install the immobilizer control unit cartridge in the scan tool.
  2. Turn OFF the ignition.
  3. Connect the scan tool.
  4. Turn ON the ignition with the key to be coded.
  5. Enter the 4-digit password that enables service personnel to use the scan tool for key coding.
  6. A lost key can be deleted only by deleting all keys and reauthorizing the remaining keys as new keys. If a key is lost, go to the next step. If no keys have been lost but an additional key is desired, go to step 8.
  7. Use the scan tool command DELETE ALL KEY CODES.
  8. Use the scan tool command AUTHORIZE ONE ADDITIONAL KEY.
  9. Repeat steps 4, 5, and 6 until the immobilizer control unit has recorded all of the new keys or, after a deletion, has reauthorized all of the remaining keys. The immobilizer control unit can record a maximum of 5 keys.
  10. Return the system to the normal mode.
  11. Turn OFF the ignition.
  12. Turn ON the ignition.
  13. Crank to start the engine.