I have a 1999 Coleman 455 Seaspray with a 51764 circuit board. I received a FLO error, so I checked the following:
1. Removed filter, still get error
2. Replaced pressure sensor, still get error

When I get the FLO error, I turn off the main breaker, wait a few and turn it back on. Turn the temp to 100 degrees and the tub heats up to 100 and the pumps turn off, within 30 seconds, the FLO error appears. I have checked continuity from the pressure sensor and I get no continuity when pump is not on, when pump is on, I get continuity. I checked this at the pressure switch and at the connector inside the control box (appears that my new pressure sensor is working properly).

I have good flow on low speed (it's a brand new pump).

I am out of ideas on how to trouble shoot this error. Anyone have any ideas on what else I could check?

Please Help!!
Thanks.