On all 2003-2007 Ford 6.0L Power Stroke diesel engines you will find the FICM bolted to the drivers side valve cover...you may need to unbolt the coolant reservoir from the 'cowl' so that you can get your arms/hands back there to work on the FICM.
You don't need to drain the coolant...just unbolt the bracket that hold the coolant reservoir, and gently move it as far out of your way as possible. Be careful, as there is a plastic coolant connector that can be cracked if the
On the top of the FICM, you will see a diamond/oval shaped metal plate...remove the two screws from that plate (Torx#20).
under that plate you will either see 7 "lugs"...or 4 "lugs" (depending on the year of the truck)...
if you have a "7 lug FICM"...you want to put one lead from your multimeter onto the upper left "lug"...and the other multimeter probe to ground (bare spot on the cylinder head, alternator bracket, negative battery terminal, etc).
If you have a "4 lug FICM"...you will want to check the lug on the right (closest to the drivers side fender).
be carefull NOT to lean the probe on the FICM lug...over onto the aluminum case...you might let the smoke out, LOL...
Have someone turn the key to the 'on' position (don't crank it yet)...and see what your FICM voltage is. It should be >46volts.
Next have someone crank the engine...and see what the FICM voltage is while cranking...again..should be >46volts.
Go ahead and start the engine...and see what the voltage is while idling.
If the FICM voltage drops below 46 volts...then it is "bad"...
we have seen FICM's as low as 17volts...some 19v's...some in the twenty's and low thirties...
obviously...the lower the voltage...the 'worse' the FICM is...and the more likely that (cold) rough running would be a result of a bad FICM.
however..if you email (or call) us and say that your FICM is dropping to 43-44volts...while low..I think that you may have some underlying injector issues that may be contributing to your cold rough running, as much as the slightly low voltage FICM
FICM testing procedure - Ford Truck Enthusiasts Forums