ABS lamp

With me, the abs display constantly lights up,I drove and had read out today at the Mitsubishi dealer and could not tell me afterwards what it is,it could be a cable oxidized or also the control unit.This reading was free if he would make the larger reading cost the 60-80€ what he means now with larger reading ,no idea it could be 100€-1000€ expensive Space runner Built 1996 what should I do??