PCMs may need to be reprogrammed for several reasons. One is
to fix factory bugs. Flaws in programing that were somehow missed but must be fixed by downloading and installing the latest "service pack." It’s a
never-ending cycle of upgrades and patches. It has become a crutch for automakers who rush products to market that aren’t quite ready. This philosophy of "build it now and fix it later"
When replacing your vehicles computer, many times they are sent without an operating system. This is done to reduce the need to have numerous different part no's for the different vehicle options. After the computer is installed the operating system that matches your vehicle's options needs to be installed.
NOT JUST DEALERS ANYMORE
Until recently, car dealers were the only ones who
had access to the tools and software needed to reflash PCMs. Thanks to the
passing of Senate Bill 1146 in September 2000, vehicles manufacturers must now make this technology available to independent repair shops.