71 Pa. Stat. § 784.6
Thereafter, when the Lieutenant Governor transmits to the General Assembly his written declaration that no disability exists, he shall resume the powers and duties of his office at the expiration of four days unless within that period the President pro tempore and a majority of the Governor's Cabinet as defined herein, transmit to the General Assembly a written declaration that the Lieutenant Governor is unable to discharge the powers and duties of his office.
Thereupon, the General Assembly shall immediately decide the issue, assembling within forty-eight hours for that purpose if not in session. If the General Assembly within twenty-one days after receipt of the latter written declaration, or if the General Assembly is not in session, within twenty-one days after the General Assembly is required to assemble, determines by two-thirds vote of each House that the Lieutenant Governor is unable to discharge the powers and duties of the office, the President pro tempore shall continue to discharge the same as Acting Lieutenant Governor; otherwise, the Lieutenant Governor shall resume the powers and duties of his office.
71 P.S. § 784.6