The Senate has scheduled a final vote Tuesday on industry-backed legislation that would limit liability against companies for Year 2000 (Y2K) computer failures. The up-or-down vote follows a procedural vote last week to lift the Democratic filibuster against the measure and bring it to the floor. Several Democratic amendments to the bill, opposed by industry, also were defeated. If the legislation passes, a House-Senate conference committee will have to reconcile it with a version that passed the House in May. Supporters of the bill are hoping to garner at least 67 votes to thwart a veto by President Clinton, who opposes both the House and Senate versions. In another action closely watched by industry, the Senate will vote today on a cloture motion to shut off debate and bring to the floor the so-called "lock-box" bill. The measure would make it more difficult for the Administration to divert dollars from the Social Security and Medicare trust funds to other programs.