He's right, I'm getting my acronyms mixed up. I had just been reading the thread about reflashing FICMs and it just stuck there...
The HFCM contains the principal water separator (the function that used to be handled in the 'bottom half' of a fuel filter/separator). You may be familiar with periodically draining off the water coalesced at the 'bottom' of the separator together with any biological detritus that made it past the tank sock -- even small traces of tank water have to be kept out of the injectors now, so the HFCM is now the first 'line of defense' (or is supposed to be).
BUT BE ADVISED that that pathetic little 'water-in-fuel' light is a dangerous thing to trust. I bought my truck used (at about 35k from Texas) and being as neurotic about water in 6.0L as i was, thought I would check 'just to be sure'. Among the many, many dubious design decisions in the Power Cerebrovascular Accident is that the water sensor in the HFCM ... corrodes when exposed to water and fuel, and when it corrodes it can come apart ... in a way that doesn't give the WIF light. It's a wise precaution, especially if you are on the road and not buying from known-good fuel sources, to periodically drain and inspect ... and at some point inspect the water-in-fuel sensor for degradation.
