I'm getting the FL1 error on my J-315. I've replaced the main pump and still get the error. After reading here on the forum, I turned off the power and removed the filters, let it stand for 15 minutes and then checked to make sure the tub was circulating water. There was nice suction with the filters out. I also pressed the + and - buttons at the same time and the F2 indicator came on (the forum indicated that this should identify whether it was the Flow Switch, F2 would indicate it is not the flow switch). I'm not sure what to do next. How do I know if the small Circ pump is working or not? Water seems to be circulating in the hot tub, but I'm not sure whether that is due to the main pump or the small circ pump. Sure wish there was a nice troubleshooting manual for the tub with locator diagrams as well as schematics!