Are you denying that the Holy Spirit promised to each of us who truly believe does not determine truth?
John 14:16 And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever; 17 Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you.
When you are in schism with Christ’s church, you do not receive that indwelling.