I have a 6 yr old Mastertemp 400 gas heater usually used in our inground pool to heat the spa but sometimes in mid winter for the pool (I'm in FL). When I turn it on, cycles ok, initially fires, then shuts off and all control board diagnostic LEDs on the board turn on solid and all touchpanel LEDs turn on with a display error code of 999. I've had other issues before that I diagnosed and fixed using the control board LEDs. This time with all the LEDs lit not sure what the problem is. This issue is not in the troubleshooting guide. I'm thinking it might be the control board but need some help to diagnose the issue before shelling out $350+ for a new board. I can do plug and play maintenance but I'm not an electronics genius. Thanks for any help you can provide.