Although Frigidaire dishwashers are renowned for their reliability and integrity, they have one little weak spot: if you have one, you should be ready to face the Er issue one day. It indicates a problem with a touch pad or keys.
Prior to replacing the touchpad, use the breaker box to reset the dishwasher breaker. Not unlikely, it will solve the problem, at least for a little while. Although it is not a panacea, it is worth trying: sometimes it solves the problem for good.
If the resetting does not work, there is hardly an option but to replace the keypad. Use the breaker box and cut off power. Undo the screws, which hold the door panel and control panel. Remove the door and the front part of the control panel. There will be a group of plug-and-play connections relating to the keypad or touchpad.
First, you can try cleaning the ribbon cable where it is connected to the main control board. Not unlikely, an eraser could be helpful. However, there is nothing to guarantee that it is going to work. If it does not, the keypad has to be replaced. It is very easy to disassemble the keypad/touchpad unit, because it uses plug-and-play connections.