Not to thread steal; I have a #3 misfire after new engine. Question: I shorted my trailer wiring and I think that's what started this. When engine was installed this would clear temporarily. We replaced the ECU and it cleared till I pulled my newly rewired trailer; after speeding up to get on the frwy the sel began to flash, then it would with scantool only temporarily till the truck is under load. We replaced the gauge cluster and POW: problem solved... Until I hooked my trailer up. The trailer wiring is correct and the towing wiring adapter in truck is new: could there be something in the circuit that is triggered when I pull my trailer?