Remove the plaques and using an old tooth brush clean with mild soap and water.. Rinse thoroughly, towel dry and finish drying them with blow drier. The interior of the unit and it's filter should also be cleaned. Depending on what type filer it uses (Aluminum mesh or soft mesh plastic) they too and can be washed with mild soap and water, rinsed and thoroughly dried. Any other type filter material may need to be replaced. Clean the interior with canned compressed air with a straw nozzle and a dry paper towel.
Of course, before you do any of the above, unplug the unit.
My unit would display e001 and e003 errors. Cleaning the filter and replacing the ceramic ozone plate did not fix it. Ended up taking the board out and inspecting it. Three capacitors were bad. After replacing, the system is working again.