from my understanding , if the check engine light is flashing , that means it is in limited power mode , which is caused by an overheat on one of the three egt sesnors , it should also say , pull over now safely on the read out , just delt with this on 550, would drive good for about ten miles and then start doing that , ended up being the last egt sensor behind the dpf filter giving false signal to ecm and causing that concern