my brothers 98 civic hatch the other day it trew a cell and now the speed ometer goes up and down like crazy, also the cell its not steady like the light dims a little but doesnt go off just dims really fast about 3 times a sec,

any one got any ideas i went to autozone to get it checked, they said that the ecu didnt link with the reader, any ideas???

fuses are ok , reseted batteries, when it happened it was normal and just started doing it ,