PEUGEOT ADBLUE DELETE - AN OVERVIEW

Given that past diagnostics / code clearing drove three miles and light back again on / motor turned off straight away ad blue filler cap removed and tried to blow/suck as a result of cap to determine if ventilated. Cap will not be ventilated. left cap off and tissue in filler neck for 80 miles/no lights came on.I’m in no situation to spend thous