Hey guys,

Recently my SGII has been reading voltage at 9v during startup. It happens intermittently, sometimes during cold or warm starts. I had each battery individually tested at the parts store and both were good, each is only about 2yrs old. FICM readings are constant at 48v, even during startup. Battery connections are clean. I want to get a handle on this before it starts affecting my FICM and all the other good stuff that low voltage affects. I have 77k mi. on the engine. Guy at the parts store said the starter could be going bad?? Engine cranks strong with no hesitation. Just would like to see what other things I can look for, since the batteries check out good.

Thanks

 

Is the PIDs right on the gauge,I do know that while glo plugs are on it will show around 13.5 as low as 10.5, is the alt stock and how old is it?

 

Whats the V-ref values?

 

Typically the voltage drops I see on the SGII range from 10.3-10.5 while cranking., then raise up to about 11.3-11.5 while the glow plugs are on, after that voltage maintains 12.5-13.0

Alternator was replaced under warranty about 3-4 years ago.

 

Not sure what you mean about "V-ref values"?

 

Vehicle Reference voltage should be =
koeo-4.9 low-4.9 high-4.9 operating range=4.5-5.5

 

I'm not too sure about that one, I don't recall seeing this on my SGII. Is this and Xgauge reading?, if so I need enter that into the SGII

 

Have you checked where the ground wires connect from the battery on each side to the frame? There is also a ground strap from the alternator mount to the frame ground cables. These are down underneath CAC tubes on both sides, top of the frame and are in the wet and salty road grime so, it's possible your grounds are playing tricks on you. If your batteries are load tested or tested by hydrometer for specific gravity, let us know what your alternator main red wire is for volts at start up, after running for a while. This should be 14.4 at start and rise to 14.8 quite quickly, ie a few minutes. The other thing you can try is charge both batteries over night and see what SG volts reads prior to start, after start like described above. My outlook monitor off OBD2 port reads 11.0 on accessory, 12.8 prior to start,11.8 to 12.0 right after start, quickly rises to 12.8, then slowly up to 13.1 to 13.2 volts. Your voltage is to low a voltage for health of FICM after start, so good you are checking things out. It will only take one bad cell across both batteries that will cause you grief, so either SPecific Gravity each cell after full charge or have someone load test the batteries and load test the alternator after checking those ground cables. Hope this helps you, let us know how you make out on all this.

 

Yes xgauge, also check out the FICM logic power and FICM vehicle power just for Giggles to see the health of the ficm

 

That actually sounds low for alt output, and even tho your batts load tested ok, they look marginal by the numbers. My guess is you have the standard output Alt that came on most 6.0s and is not up to the task. So, if I were in your shoes (seat?!) I'd be looking at a 140A Alt at a minimum and if you run a honkin' stereo or any other big power user, go even bigger than that -- You should be seeing High 13s for Volts at the ODBII when all is stable and running and low 14s at the Alt -- otherwise your Batts are not getting fully charged and are crying for help..

I would replace both Batts with new ones 850CCA or more at the time you do the Alt. Meanwhile try keeping your truck on a smart charger for a while, particularly one that has a desulfating phase.

Scott: where were you going with the Vref? I'm not up on what that would tell me I guess, unless there were other crazy readings -- tho I do watch mine....

 

Just an over all Vehicle power point, he really needs to look at the Alt ,Batteries and Ficm main lp and vp. I was woundering if the V- ref was low as well.

 

He should measure battery voltage with a digital meter to verify the real voltage. You will get diff voltages via odb, fussed power circuit, and battery directly.

Using meter get voltage when you get home at end of day:
with engine, high beams & a/c fan on high, then with lights and fan off.
Shut off engine, read batt voltage.

Measure voltage again, in am before turning key then immediately after starting, and then once glow plugs go off..

Sent from my Sprint PC36100 using IB AutoGroup

 

My OBD port reads low, it always has since new installation. My alt reads 14.4 up to 14.8. Voltages I listed are of the main voltage reading at the obd2 port. I have had this on the truck for 7 years, voltage never goes above 13.2 when running. I have 850 CCA batteries that are two years old, and I have a stock 140 amp upgraded alternator but it is original. Then again, it's never read over 13.2 at the OBD-2 and never over that at the batteries either. The batteries pull down the voltage as a buffer. I don't know how any of you can get hi 13s or even 14 from your obd2. If I get a new alternator, I will be getting a 185 or 200 amp, then we will see what I get for obd2 voltage. I know my alternator is working cause I can put a charge on my batteries and on trickle, they are full in less than 15 minutes.

 

Thanks guys, I will work with the info you gave me and see what I can come up with in the next few days.

I appreciate the feedback!!

 

I get 13.5 and 14 at full charge at the port even with my stock same alt since 04 ( dam I hope I didn't jinxs my alt).