no comunication with abs control unit – punto 188

hello people, since a week the abs light goes on at our punto 188 mod. 2004 sometimes only after a few (100) meters drive on, sometimes directly after start (or stays directly on). abs does not regulate with every brake, the phenomenon seems to exist. so no regular intervention, but light on. have a diagnostic interface and the 3 adapters to adjust the pin placement, use fiatecuscan test version. come into the motor and airbag control unit (airbag light was also now on, spora discher fehler am beifahrerairbag-ausschalter *grr*), however, can not establish a connection to the abs-controller. I have already for 6 hours the battery clamped off, but then I did not have to re-enter the radio code (orig. blaupunkt cd-radio in punto-look). was the battery therefore not long enough or why do I not get into the control unit? thank you already for pointing out!