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That may be a call to the dealer, if you have the 2006, you can pull the numbers off the side they should be able to tell if it will work in a 2008 system. This is a gray void when trying to go out of year components in the electronics area, upward or backward compatibility with all the other items. If it hasn't been reset default to new install a trip to a GM dealer is needed to reprogram it, depending where you live $70-100 is the range. I got a 07 unit and so no issues with it in my 2007, a few listed on eBay pretty much say it needs to match what you are replacing. The VCIM is the same problem except for a wider range of years and other GM makes in case you want the Bluetooth upgrade later.