Catalyzes the dephosphorylation and concomitant reactivation of the E1 alpha subunit (PDA1) of the pyruvate dehydrogenase complex. H2O + O-phospho-L-seryl-[pyruvate dehydrogenase E1 alpha subunit] = L-seryl-[pyruvate dehydrogenase E1 alpha subunit] + phosphate Binds 2 magnesium or manganese ions per subunit. Processed by mitochondrial inner membrane protease (IMP) complex and released to the intermembrane space. Present with 7550 molecules/cell in log phase SD medium. Belongs to the PP2C family.