Mystery Furuno proprietary nmea sentence

I'm working through a bug in my system and have come across a sentence I can't find any documentation on.

$PFEC, idfnc, R,4*3c

Is this an error message or what?

Any help would be much appreciated.

Johnsonsf-
It would be extremely helpful if you could provide us with which instruments you observe this sentence.

I'm seeing it through a Brookhouseonline wifi multiplexer on my iPad. The network includes; Furuno GPS chartplotter/radar, Garmin GPS, B&G depth, wind, speed, Furuno AIS receiver, all attached to a SeatalkNG network of Raymarine i70 displays via an Actisense NMEA 0183 to 2000 converter

Yes, that is a Proprietary sentence, but should not have any affect on the network.
What bug are you experiencing?

The i70 instruments at the helm are losing all data after running for a few minutes. There's one more in the nav station that goes down too at the same time. All data quits, but if I unplug the Seatalk cable to the helm the data comes back to the one at the nav station. I thought there might be a sentence conflict and hadn't seen the PFEC sentence before. I thought that might have some info about a conflict.

Everything was working fine after i added them and the actisence converter to the network six months ago and then one day about two weeks ago after I had been anchored for a week (I'm cruising in Fiji) I turned on the network and boom, problem. I've tried isolating each of the helm instruments one at a time, but the same thing happens so I don't think it's an instrument gone bad.

Most manufacturer s use proprietary sentences and if not used by the system, they are ignored. That isn’t your problem. Intermittent problems are the worst.

Thank you. I didn't have detail of what those sentences did, so very useful.

And the good news is I just found the problem. After testing everything one piece at a time, I finally discovered a defective SeaTalk NG connector tee. Replaced that and the system is back running without the hiccups. Yay.