You need:
GM Tech2 scan tool (Original $2000 -$3000, $246 in www.fobdii.com)
A laptop or pc running windows xp home
TIS 2000 software CD and USB key (GM Tech2 alone is a scanner, with TIS2000 CD, you are able to do programming)

GM Tech2 scanner Features:

1) GM software in the Tech 2 Flash means the most comprehensive diagnostic software available for late model GM vehicles.
2) Support for on-board diagnostics on all GM systems 1992 thru current year.
3) Removable hardware modules provide insurance against scan tool obsolescence.
4) Large, easy-to-read backlit screen.
5) RS232 & RS485 ports provide the avenue to connect future devices to your Tech 2 Flash.
6) Ability to capture stored DTCs, Freeze Frame, and Failure Record for later review.
7) Ability to view the status of vehicle diagnostic tests as they run.
8) Bi-directional The authentic GM 1992-current year software will provide full bi-directional control when performing power train, chassis, and body diagnostics.
 
Make sure your vehicle is included in the vehicle coverage in order to carry out the process smoothly please. (GM TECH2 Scanner with TIS2000 works better vehicle before 2007 year)

–Insert the Tech II scanner TIS 2000 CD into the computer, Tis2000 helps to get the latest calibration for the PCM
–Connect your Tech2 scan tool with laptop with a RS232 pass-thru interface
–Start the GM recalibration software program on your PC and welcome the vehicle information (year, make, model, etc.) program
— Connect the Tech 2 scan tool into the vehicle’s diagnostic socket
–Turn the deice ignition switch on and wait for the start screen
–Confirm the vehicle VIN number
— Choose the operating system, engine, fuel system, speedometer or transmission.
— Select “normal reprogramming” or “VCI” (special modifications).
— Choose the update bulletin/recalibration number from the menu.
–The system now starts transferring data. It will last about 3 minutes. You will notice that the PC screen will display a blue progress bar as the software is uploading to the vehicle. (The GM setup will not allow the same calibration to be reinstalled over itself. Only an updated calibration can be loaded into the vehicle computer.)
–When the system completes loading software, the windows will pops out “PROGRAMMING COMPLETE” message.
–Turn off the GM Tech2 scanner ignition and disconnect it from the vehicle.