i have a p28 ecu and it trips once in a while... it'll be cool, normal no check engine no codes, then sometimes it will throw a check engine and will idle at 2000 even when warm. i try to get the codes by crossing the wires but it doesnt flash, it just stays on! any ideas why it does this?! then it will go back to normal after a few starts, but it it starts trippin agin......

 

Honestly, sounds like a bum ecu... That or you have a bad connection somewhere...