03 Sterling acterra 3126 no start

Have an 03 sterling acterra with a cat 3126 that will not start after sitting overnight. Once it starts, it will start all day fine. Thought it was oil or fuel related. But went out this morning to start it and the dash shows 3.3v, and the check engine light and intake heater light will flash randomly. It cranks over fine, batteries are charged at 12.6v. Unhooked the intake heater battery cable thinking it was drawing down too much, no change. All fuses in the engine bay have 10.8v to them. Thought it wasnt getting enough battery voltage to the fuse panel. Went to grab a set of jumper cables, but before I hooked it up to the solenoid under the fuse panel the dash was reading 12.6v and the lights stopped flashing and it starts fine now, even with the intake heater unplugged. So I am pretty sure it is a connection issue, but I have no idea where to start now that its working fine again.