How to program a new ECM?

The first thing you will need is either a scan tool that can do programming online or a laptop that can access the GM Techline Connect website. Next you need the J2534 pass-through device. That can either be a stand-alone unit like a Bosch Mastertech 2 or a Cardaq2 or 3 Or a GM MDI that acts as the J2534 and the scan tool interface. Now with either method you follow the setup for programming a module, a big one is that the power CANNOT drop out under any circumstance while programming a module. So, you want a battery maintainer on the vehicle so that the voltage says between 12 and 15 volts while you work, if the voltage drops or goes off you buy a new ECU and start over. Lastly you want a copy of the option sheet for your car, this is because while you might know you have the up-level radio, GM will ask for the actual option code if they used more than one version. Now you have the tools, connect the battery maintainer and the scan tool or laptop. Next connect to the GM Techline using the internet. You create an account and get a set number of VIN tickets. Now you access your account and go to programming. Enter in the vehicles VIN and select which modules you need to program, check all of them because there are times that the latest software for a module requires another module be updated as well.
Now you follow the on screen prompts to program the module. This is where it can be interesting because depending on the time and the module and your hardware it can take a few minutes or hours to do the full programming, this is because it may tell you to cycle the key or the shifter or even open and close a door during the process. Now once it's done and the GM connection shows everything is correct you then start the engine and test ALL options and devices on the vehicle. Then you can disconnect the tools and go through and erase any trouble codes that may have set during the process. Now the bigger question is, are you planning on doing programming a lot or is it a once or twice a year thing? If you plan on doing it professionally then buy the hardware to do it, expect that to run between $3-$4 K on the initial purchase or more depending on the set up. If you are only doing a single module every few years you might want to have it taken to a shop that does programming and pay them for the process rather than buy all the tools that you have to keep updated, even if you are not using them.