OH = Sensors reading 112-118 Degrees. The OH error code is show due to overheat. A dirty or worn out filter can cause several error codes to be displayed. “OH” (over heat) because water is not moving quickly enough through the heater vessel and the high limit detects too hot of water temperature. Check the filter. The spa is most likely heating up past the set temp due to a pump that is most likely running continuously due a filter cycle setting being set for too long. But if there is nothing overheating and water is cool then this error is related to control board of the spa,In other case the filter has to be checked also checked the fitting of new pump to the filter.If the pump is not fitted properly then this can result. If in-case you get SN error then this is related to temperature sensor. Thanks. keep updated for any more query.you can rate this solution and show your appreciation.