What is a technical service bulletin? The wiki page describes it pretty well.

Technical Service Bulletins, or TSBs, are recommended procedures for repairing vehicles. Not to be confused with recalls, a TSB is issued by a vehicle manufacturer when there are several occurrences of an unanticipated problem. TSBs can range from vehicle-specific to covering entire product lines and break down the specified repair into a step-by-step process. While sometimes written by engineers employed by OEM's, the majority are authored by the first automotive technician to come up with a repair procedure. Because certain problems may have more than one cause or there are sometimes more than one way to fix a problem, it's somewhat common for there to be more than one TSB for the same problem.
Below is a list of the TSBs for all model years. They are not the complete reports, but just titles that hopefully help out. I highly suggest using the search function as the list isn't the shortest. To get full reports you'll need to register (and pay) on a number of sites that offer them. A few are:
AllDataDIY.com
ACDelco Technical Delivery System