My dive computer is displaying "bsl" or "651", do I need to return the unit for factory service?

No, the "bsl" diagnostic code is field serviceable, and does not require the unit to be returned to the factory. "BSL" stands for Boot Strap Loader, which is the programming mode used here at the factory to upload firmware into the dive computer. There is a specific combination of button pushes used to place each computer model into this programming mode. While the computer is in BSL mode, the computer will not accept any other commands. It is possible to inadvertently access the BSL mode by accidentally pressing the correct combination of buttons, but it is simple to exit this mode. While most computers will automatically return to normal mode after 2 hours, depending on the model and firmware of the computer, you may need to manually reset the unit. To manually clear the BSL mode, simply remove (for approximately 10 minutes) and reinstall the battery. Doing so will reset the computer and restore normal function. Note that all settings, including date, time, and decompression status will be lost once the computer is cleared. However, the dive history, and downloadable memory will be retained.