DML FAQ : General : Are TSBs provided free of charge even after the warranty is up?
Once the warranty is up, TSBs cost. They're not like recalls, which are critical, safety-related problems. The manufacturer is not required to inform owners of them.
A TSB is basically a communication from HQ to the dealers saying "we've had numerous reports of this particular problem - here are the symptoms and fixes." Service departments typically won't apply a TSB unless they've found it while diagnosing a problem and they can match up the symptoms.