hi my belling dishwasher is saying jj and is blocked ?

My belling idw603 diswasher is saying jj when trun on the water from the mains is going straight out the drain pipe I clean the filter and the bottom plate but when I trun on the diswasher the water stay inn the filter and it won't change programme for me it makeing bussin g noise and the water keep pumpin g out the drain Pipe if annyone had this problem how did they fix it liam thank