When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
If all you want to do is read engine or power train codes then a simple OBDII scanner or the two tuning packages will let you do that. However, if you want to be able to see the remaining 45% of codes that can show up on a C6 then you need a more capable scanner such as a Tech 2 or something of similar capability. Lowest cost samples of those can be in the $450 range plus the cost of the laptop to run them on.
You can go to many auto parts stores and they'll check for DTC's for you for free. Just attach the tool to your OBDII port under the steering column.
You can get your own code scanner for less than $100 at many auto parts stores - I got one of mine at Walmart for about $79, and it works really great!!
Like Bill says, you won't be able to read ALL codes, but most all the common ones.
Make sure any code scanning tool you use or buy is "CAN capable" or it won't work with the OBDII system and circuits in our C6's.