Posted this over in the Excursion forum also.

About a month or so ago I went out to the Ex and went to start it. Cranked and cranked but no start. Left it and went to work and tried again the next day. No start. Temps were low 40's in the morning. About a week after that, the weather warmed a bit, and the Ex started right up. Huh... So I got a code scanner and sure enough, low voltage to all 8 cylinders. Damn I thought, the FICM is going bad. So I researched on here and the powerstroke forum about fixing or diagnosing for sure the problem and how to fix it. Well, since then the truck starts just fine. Cranks a little long but does start. So yesterday, I got a Edge Insight at my local mechanic and installed it. Here's what I got:

On run but no start: FICM voltage is 47.5-48
Battery volts vary as low as 10.6 to 11.2

During start: FICM stays at 47.5-48
Battery volts stay 10.4 - 10.6

Driving: FICM stays as above
Battery volts 12.3 to 12.9

I'm thinking my FICM is OK but I need new batteries? It's warmer now so the truck is starting fine. RIght track?

Other thing, a while back I posted about rear drive line vibration in my Ex. Got a new rear drive line built, transfer case serviced, rear diff fluids changed (found I had 4.56 gears). Also found the truck I bought at a stealer "used" to be lifted but was returned to semi stock height. Turns out the drive line angle to the rear diff was off. Got shimmed, new U-Bolts and no drive line noise. Got lucky on that one I guess.

 

OH ya you better get your truck a set of batts, before FICM takes a hit too then Inject.that tool mite of just saved you a pile of cash

 

whats alt reading?

 

10.4V?
Your batteries are definately shot!

 

Just be aware that proper FICM voltages does not guarantee that the FICM has not failed .....

 

I agree. Time for new batteries.
Bad batteries will show it the most when it cold.
Also check and clean the cabled on both ends.
The grounds too.

Sean