Po731 Po740 Po4o3

Just Found This Site And I Thinh Its Awesome. Ok I Got These Codes From A Engine Check I Know The Po403 Is The Egr Trans Circuilt Open Or Shorted.the Other 2 Codes Are Also For The Transmission.i Had A Rebuilt Transmission Put In About 3 Years Ago.well As For My ??? Any Of These Codes Could I Fix.i Am No Car Mechanic But Was A Helicopter Mechanic.sooo I Dont Know What Exactly These Codes Mean And What Exactly Needs To Be Replaced.i Know If I Go To The Pro's There Gonna Wack Me Parts And Big Bucks For Labor.and Just Trying To Save Some $$$$.any Replys Greatly Appreciated