Catalyzes the second two steps of the methylation pathway of phosphatidylcholine biosynthesis, the SAM-dependent methylation of phosphatidylmonomethylethanolamine (PMME) to phosphatidyldimethylethanolamine (PDME) and of PDME to phosphatidylcholine (PC). 1,2-diacyl-sn-glycero-3-phospho-N-methylethanolamine + S-adenosyl-L-methionine = 1,2-diacyl-sn-glycero-3-phospho-N,N-dimethylethanolamine + H(+) + S-adenosyl-L-homocysteine 1,2-diacyl-sn-glycero-3-phospho-N,N-dimethylethanolamine + S-adenosyl-L-methionine = a 1,2-diacyl-sn-glycero-3-phosphocholine + H(+) + S-adenosyl-L-homocysteine Phospholipid metabolism; phosphatidylcholine biosynthesis. No visible phenotype under normal growth conditions. Belongs to the class VI-like SAM-binding methyltransferase superfamily. PEMT/PEM2 methyltransferase family. Truncated N-terminus.