Catalyzes the dephosphorylation of diacylglycerol diphosphate (DGPP) to phosphatidate (PA) and the subsequent dephosphorylation of PA to diacylglycerol (DAG). Together with DPP1, regulates intracellular DGPP and PA levels which are phospholipid molecules believed to play a signaling role in stress response. Can also use lysophosphatidic acid (LPA) as a substrate. Substrate preference is PA > DGPP > LPA