[Coach73]

Ok, having an issue. I just replaced both batteries with factory motorcraft 850CCA. On my scangauge I'm noticing low FICM supply and output voltage (Supply down to 10.5, output down to 46.5). I also noticed that my batt voltage is dropping to 10.5 as well. This is only momentary, it comes back up as soon as the truck starts also it is cool in the morning so the glow plugs are working. I cleaned the terminals when I put the new batts in. Someone mentioned the FICM relay could have excessive voltage drop across the contacts. I'm at a loss here, HELP!!! Coach

 

[RRF985]

So you are showing 10.5V when cranking during start? That doesn't seem that bad to me. If you are maintaining 46.5V on the FICM during that time IMO you're fine.

 

[Coach73]

Yep, that's what I'm seeing. As soon as it starts batt voltage climbs to 11.5 or so, FICM volts about 47 until alt. kicks in. Thanks. Coach