I have a 2005 f250 stock tuned with 154,000 miles. I'm showing code P0611 and P0231. I had a buddy to scan it, at operating temperature the FICM with occasionally drops to 45.5 volts. The only issue i'm having is a miss from half throttle to full power.
The stock ficm, in my opinion, is one of the weak links in the 6.0L woes. Sending it out, or replacing it with an aftermarket replacement is just good insurance, as I look at it. Ed at FICMRepair.com - FORD Powerstroke 6.0 FICM Repair, PHP Tuning and Truck Parts is the best. Have a look at his site, there is a lot of good info and insight on the ficm. Also make sure your batteries and charging system are up to snuff, as these are crucial to ficm longevity. Good luck.
P0611 is definitely an FICM code. I had that code intermittently for over a year before my FICM finally went totally wonky. Sometimes it would go weeks without setting it, other times I'd get it at every startup five times in one day. Talk to Ed, have him fix it so it won't ever break again. Maybe the best money you can spend on your 6.0.