Loss of power after 15 minutes even when parked.

Question

Loss of power while driving or parked. New ECM. New Crank shaft sensor. New o2 sensors (all). Engine sounds like new. Runs great until power loss. Will run for 12-15 minutes when started cold. Always the same time frame. p0871 and p0841 are the only remaining codes. But I have had those for years.

Answer 1

P0871 OD pressure switch sense circuit

P0841 LR pressure switch sense circuit

With code P0841 and you loose power just in park or drive within 15 minute you have a loss of prime. The more likely problem  is the transmission pump. . in order to set these codes the transmission begins slip.when you go forward in gear,