The FICM multiplies the battery voltage by 4x. Low batteries WILL cause your FICM voltage to read low, and 12.5 volts is low with the vehicle running. What is the FICM main power/logic voltage?

 

My alternator at idle will put out right at 13.0 volts with my AC cranked. Just remember that your glow plugs will still be active for about 60-90 seconds after you start your engine. During that time, my voltage is roughly 11.5 volts. Your alternator MIGHT be getting a bit old and not performing well, but it should be plenty for your FICM to maintain 48v. Your FICM needs to be repaired.

 

Exactly. Voltage-wise my truck does the exact same at startup, though my FICM is on it's way out.

 

While swapping out the tranny fluid/filters/etc... I put the batteries on a charger and cleaned up the connections.

Once I was finished, I took the vehicle out for a drive. Stats on the FICM voltages:

At key on engine off: vehicle = 12.5 V, FVP,FLP = 12.5V, FMP = 48V
After a few minutes of idling: vehicle = 13.5V, FLP.FVP = 13 - 13.5 V, FMP = 30V
I did notice after driving quite a while the FMP would come up to the mid 40s, even up to 48V. However, it appears to drop off when you get into the throttle. Guess this eans new FICM in my future

Is the upgraded 58V FICM worth it? What is the benefit if you are using the truck for pretty limited camper towing duty?

Thanks to all for your replies...

MikeB

 

Yes, get a 58v FICM upgrade.

 

The question above is why get the 58V FICM upgrade?

 

I was in the exact same situation about a month ago... bad FICM. I went with Swamps 58 volt and everything's back to normal. I did a lot of research prior to going with the 58 volt and the conclusion is that you should have zero problems towing your camper with the upgraded module.

 

Thanks to all for the replies. I have been keeping a closer eye on the voltage, and it appears to reach up to 48V part of the time. Is there any risk if I wait until the FICM really bombs out? Will it damage the injectors? Right now I do not see any driveability issues with the vehicle.

Thanks again for all the replies.

MikeB

 

Don't wait, as it will get worse and will eventually damage your injectors. The hardest time on the FICM is at cold startup, and that's when a failing FICM usually shows itself (voltage-wise). As others have said, it will also leave you stranded some day. I'm taking mine in under warranty next week, as my FICM is also going south....

 

Yes, it could cause injector failures or it could just not start and leave you stranded.

 

So I have a quick question for you guys and didnt exactly want to start a new thread. But my ficm is a steady 47-46.5 while running. The past couple days it has dropped to 45 two or 3 times, twice while cruising on the highway.

Now my battery voltage is around 13.1 and drops frequently to the high 12s. Now Like many people have said, a cold start will show a bad ficm but even mine when cranking wont go below 46.5 cold. Does this mean my batteries are going or is it a bad ficm? Thanks for any helps guys.

 

^^ I would say 'yes'. About a year before my FICM went bad, I lost a battery and had some of the same symptoms at startup as a bad FICM. The only thing to counter this is that a bad battery generally means low voltage going into FICM which in turns means your FICM voltage will suffer significantly. My battery voltage drops to high 12's once in a while too... especially at idle. If it continues to do this while under throttle, I would investigate the alternator. You will generally get a battery light coming on if it starts producing low voltage. Hope this helps.

 

The alternator needs to be replaced with one of higher amperage I bought my 03 new and the factory alternator gave me problems for many years until I replaced with a 280amp truc k has 270thousand miles bulletproof at 145 and still runing on factory turbo fuel injectors ficm pcm will be replacing the ficm with a 48v and a 40horse tune and bigger oem injectors to get better towing capability and better fuel mileage maintenance guys is the secret and rotella t4 oem filters God bless you all

 

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