On what? It helps if you give all the info such as make & model number. PU usually means pump fault such as when you have a blockage & the water is draining too slowly or not at all. In your case it can't mean that because yours is over filling. PU & over filling would suggest to me a faulty pressure sensor but without knowing your make & model I can't be sure or tell you where that is.
Lincoln Appliance NZ, September 2011
