Question for the gurus. Is this a FICM problem or battery, charging system error? Batteries are 2 years old. FICM output voltage varies from 47.5 to 48.0 VDC. FICM logic circuit and vehicle power read from FICM pics display voltage dropping to 10.5 before recovering to about 13 vdc after about a minute.

This has been an off and on issue for several years, before and after new batteries.

Thanks for your input.

 

I'd vote for loose or corroded battery connections. I'd also make sure your alternator is indeed charging like it should too. The stock one on my '05 failed December 2013 and just wouldn't charge the batteries. It would keep them alive at 11-12 volts, but that was it.

 

Have you load tested your batteries? Usually they'll do it for free at places like AutoZone.

 

I am on 12 hour shifts for a few more days, I will look into another load check. Have not done one in a couple of years. I did look at the terminals before posting. They look clean, but I may take an indian head to them. System charging volts says 13.3 - 13.5 VDC.

 

Well this morning told the story. After thinking things through, the supply voltage, 12vdc, comes right off the drivers side battery. Back a few years ago the tab lug broke and I had to crimp on a different lug and added a piece of stainless steel as a mount. It is attached to the battery lug.

I remembered this at work last night. So on my list to do before going to bed was to inspect and clean the terminal. Leaving work and getting into my truck, in went the key, over to key on, engine off, glow plugs, injector buzz, start.....click.. Click,click,click....

SIGH.......

Pop the hood and go to the driver side battery to find it loose. Spinnable by hand and surely easy enough to lift off by hand. So after some abrasion to the lug and terminal and a jump start while monitoring FICM supply voltage, FICM logic circuit voltage, FICM output voltage, and charging volts I found, respectively:

13.0 vdc, 13 vdc, 47.5 vdc, and 13.7 vdc.

Later today, after some sleep, I have a date with an Indian head, a wire brush, and a wrench....

K.I.S.S. Keep It Simple Stupid!! Problem solved.

Eric

 

Good to hear. I love the simple fixes.

 

Well I got a chance to look at it. The driver side positive battery cable lug is split. That would be my charging and voltage issue. I put a small metal C clamp on the lug and secured the split halves on the battery post.

I jumped the truck and took it for about a 20 mile spin. Battery appears to be taking a charge but how well I don't know. I will be up all night on my day (night) off before going back to bed early this morning.

I won a solar battery charger/maintainer at a yankee swap. I set that up plugged into my power point in the cab. A motion activated lamp I put in at the head of my driveway keeps coming on with the wind we are having which is blowing the tree branches Near it around and routinely causing the light to come on.

I found that the light is just enough and creating a charge, which is a bonus. Supposed to be a clear night and day tomorrow with wind so the light is going to be on and off all night.

While I am sleeping, hopefully the charger will continue to work on the battery. Bright sun light will certainly help. Still it may be time for new batteries and definitely a lug.

Eric

 

What is an Indian head? Some sort of brush? Glad you tracked down your issue before it fragged your FICM. Some of us are not so lucky!

 

The Indian head is a battery terminal brush. Someone I knew called it that and it just stuck. I tore apart my FICM a couple of years ago and removed and replaced any poor quality solder joints with 63\37 rosin core solder. The repair has been a good one. The FICM is still good.

Do not want to take the FICM out because of a crappy $5 connection!!

 

I hear you there, the PO on my truck never cleaned or did any sort of battery maintenance, and I believe that is why my FICM was 36v. So it's nice to see that you where able to avoid that bullet this time. Just trying to spin a silver lining for you

 

I appreciate that!! Thank you!

 

So, about $400 everything is nearly fixed. I bought 2 new batteries as at least one was not taking a charge, or very little of one, and a new positive battery cable.

The positive battery cable was a bit more involved than I expected! Running from the driverside to the passenger side battery with taps for the starter and FICM amoung other things! The cable is expensive to buy from the dealer or local auto parts places, varying from $130 - $170.

And because of the large crimped lug on the driverside, the clamp was not going to be something that could be clipped off and an aftermarket clamp put on. I am a firm believer in putting the right stuff back in sooo..

Tousley (Auto Nation) has it for 87 and some change. That was a nice savings so I bought one from them. I expect that in a few days and will install that.

Got to hand it to my Edge and Torque App. They both pointed to an issue and made it pretty easy to figure out what it was. (After some thought and a quick post here!!) Still not sure how that lug cracked the way it did, at this point it doesn't matter.

I am sure they saved me $$$! Possibility of a tow, (AND we are heading to Washington DC next week with our fifth wheel) price of a new FICM plus batteries and a cable. Alot more than $400 for sure!

SO! If you are seeing P1378....check your FICM supply voltage starting with the passenger side battery positive terminal to the Driverside Positive terminal and FICM power lead from the Driverside Positive Terminal to the FICM. An easy check that could save you some bucks!

Eric