I am getting 3 cylinder circuit low code and my F250. I checked the wire harness and did not find any chaffing, checked the FICM and it reads 47.9 to 48.5 volts running so it is not a bad FICM.
A low circuit code can mean any of these .... wiring, a connector, the injector itself, or the FICM. That is why it is always a good idea to check the wiring for chaffing, look the connectors over, and verify that the FICM connectors are fully snapped in before buying a new injector. I agree that the FICM will usually thorugh more than one injector code, but not always.
Well I finally got the time to check the #3 injector, Let me tell you what a PINA. After getting the stuff out of the way to even get the injector it went smoother (except for the bolts close to the evaporator)
Upon removing the injector I got a real good look at the plug and It was really dirty, already there I just replaced it anyway. Getting it all back together she fired up after the second try (chugged and smoked at first) and ran smooth after getting all the air out.
She is running like a champ now and no codes.
It did take me all day to complete the task but I save myself big bucks