[Robert Coats]

At Honda, there are three levels, and all are typically triggered by a team of engineers who monitor and investigate warranty claims and service records. If a particular problem starts to spike or increase, it gets under a microscope. If a real defect is found, the questions start: safety related or not? How many? Any other related issues, etc. A serial number range is determined and as needed, and one of three documents are issued:

Service Bulletin: A non-safety issue. May require a revision to a part design and replacement, or non-part repair procedure. Affected units with the described problem are repaired under warranty.

Product Update: Identical to Service Bulletin, but to ensure customer satisfaction, units out of warranty are frequently repaired at no or reduced cost to the customer. Subject to age of the affected unit and how long out of warranty.

Safety Recall: A safety issue. All units in the affected range are to be repaired at no cost, regardless of the age. Manufacturer must mail notices to all affected customers, publish notices in print, distribute notices to dealers, and report all progress to the Feds.

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Caveat: I work for Honda, but the preceding was my opinion alone.