Changed my oil this weekend and within 100 miles of driving my check engine light came on. Thought maybe it had to do with the oil change, but when I checked the codes (P0261, P0264, P0267, P0270, P0273, P0276, P0279, P0282) it was a low circuit on all 8 cylinders. The truck is running EXACTLY as normal. No long crank, no misfiring, absolutely nothing is different. I tried clearing the codes and they all came back the following day. All 8 injectors were replaced 3 years ago so I can't imagine it's an injector issue. Batteries are both 1 year old and I just replaced the alternator 2 weeks ago. The alternator was failing for about a week before I replaced it so I'm not sure if that has anything to do with it. ICP seems like it may be low but never monitored it before so I don't know what it was prior. 1.1 at idle and 1.5/6 at 2000 rpm. According to my sct the FICM is reading 48.0v key on and 31/32v at idle. All the threads that I have read related to this issue all have cold starts or rough idling. I guess that may come for me, but right now everything is normal. Any thoughts or recommendations?