Technical Service Bulletins, or TSBs, are recommended procedures for repairing vehicles. They are a form of diagnosis. 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 OEMs, 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 and there is 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.