Catalyzes the methylation of C-11 in precorrin-4 to form precorrin-5. precorrin-4 + S-adenosyl-L-methionine = precorrin-5 + S-adenosyl-L-homocysteine Cofactor biosynthesis; adenosylcobalamin biosynthesis; cob(II)yrinate a,c-diamide from precorrin-2 (aerobic route): step 4/10. Belongs to the precorrin methyltransferase family.