Can A Weak Battery Cause You To Lose Tune? How Do You Know If FICM Bad?

[LTRMC02]

I had noticed a weak start the past few days and got my truck checked and had a bad battery. I had also noticed around the time of that weak start that my truck ran different, less power and softer shift I put a new battery in the truck today and downloaded my tune again which did get back the firm shifts and maybe a little power but nothing like it was a week ago. I hear that low voltage is a killer for the FICM so what symthoms do you see with a bad FICM? The truck doesn't skip or run rough just doesn't seem to be spooling up quick like it was last week before noticing the weak starts. Also noticing the turbo fart when I got on it a few times today and hadn't been hearing that before?

[LTRMC02]

[amdriven2liv]

FICM links for testing.

FICM testing procedure - Ford Truck Enthusiasts Forums

http://www.fordtechservice.dealercon...FICM_Guide.pdf

Detailed FICM Repair Procedure - Ford Truck Enthusiasts Forums

[Chango]

check the link in my sig under troubleshooting a no start condition. Looks like amdriven has you taken care of though

[LTRMC02]

Thanks guys, that seems to be a well described repair procedure, may give it a try if mine doesn't check out good.

[LTRMC02]

Originally Posted by amdriven2liv

FICM links for testing.

FICM testing procedure - Ford Truck Enthusiasts Forums

http://www.fordtechservice.dealercon...FICM_Guide.pdf

Detailed FICM Repair Procedure - Ford Truck Enthusiasts Forums

Looking at the two different procedures for checking the FICM, ones says to unplug your glow plug module and the other doesn't. If I unplug the module then my voltage doesn't change much from the 48V even while turning the starter but if the glow plugs are pulling current my voltage will drop from 48V to 23V but will return to near 48V once the truck is running or the glow pulgs have warmed up. Does this sound like a problem or normal?

[amdriven2liv]

From all that I read in this thread:

FICM testing procedure - Ford Truck Enthusiasts Forums

It sounds like the drop in volts with the glow plugs connected, should not happen with a good FICM.

Here is a video of checking the FICM. They do not mention disconnecting the glow plugs. And you can see that their volts didn't drop when key is turned on.

YouTube - Ford 6.0 FICM Testing & Removal Instructional Video

[chancegrayl]

I had the same issue with my truck turned out to be a bad FICM, but im not an expert,

[PGreenSVT]

Yup, I suspect your FICM is ready for a rebuild. Send it to Swamps.

[LTRMC02]

Originally Posted by PGreenSVT

Yup, I suspect your FICM is ready for a rebuild. Send it to Swamps.

For the past week the truck has seemed to run stronger than it did when I posted this thread but it doesn't seem to have that "on\off" feel of power like before where you ease into the throttle and when it hits a certain point it's like hitting the power band in a two-stroke dirt bike. It's now just a smooth power curve and much better than stock but not sure it's making the power it was before the battery issue.

Much of what I've read is that when the FICM is failing then starting becomes an issue but it has started great since putting a new battery in it and it runs smooth and gives no signs of anything wrong, just feels a bit different than before. I may drive it another week and do that voltage test again. My batteries were at 12.42 volts before trying that test and the procedure claimed possible inaccurate readings if below 12.5 volts?