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I will be driving down the road and after 20 mins of driving my ficm voltage will drop to 44.5 volts or so then climb back to normal and it only seems to happen going down the hwy. It is with in spec like when the key on and on start up. its an 05 with head studs and egr delete done to it.
Good job! You caught it before it left you stranded somewhere. Another fine example of why you should have a insert your OBDII monitor name here In your truck .
So what exactly is the threshold for criticality on these things?
For example, my FICM voltage oscillate from 45.5(rare occasion of 45) to 48.5 while driving. This is withing operating range, but would it be considered a warning sign? It hasn't changed since I've owned the truck, and it's one of the four Xgauges I keep on religiously.
Low or old batteries can kill a FICM. While they may crank the engine, the crank voltage drops too low and the FICM self-destructs trying to make up for it.
If your batteries are more than three years old, either take them out and condition them, or better yet, replace them. The FICM is remarkably intolerant of old batteries.
If my FICM even saw 45 volts I would send it out for some loving. Unless it was due to low battery voltage and the battery problem was corrected immediately and the voltage returned to 47.5 - 48.5 then I may let it go.
Yup, 45v or less () it's on it's way out, if battery voltage is drooping badly during crank it might "save" the FICM to replace the batteries as Blaine posted above but it's definitely stressing.
Just replaced my ficm. I highly recommend ed @ ficmrepair.com. Many, many people here have used him. He has different options as far as warrenty and tuning on them. They are plug and play so no need to go to the dealer afterwards for tuning.
And update in the alternator is also recommended by ED. I believe he recommends the DC power 270 Xl or something. It keeps volts in check at start up even in the cold and makes them live.