have a 211, car intermittently gets a DLFB fault. it was about once a month for 3-4 months. we replaced the cartop board, changed bottom limit switch, checked all valve wiring. still the problem continued. finally replaced the main cpu/io board. problem goes away for 5 months, and then it starts again. any ideas. strange, the mechanic indicates that he has a few of these units within a 20 mile radius that seem to get this same fault intermittently, wondering if it is software related

I don't know if its software related but you might have a low-pressure switch acting up. I believe that driver is off that line I dont have the prints in front of me.

Ah Yes Down Leveling Feedback Pilot Fault....L4s bottom directional is opening while sitting at the bottom landing..had this recently..made adjustments to the cam underneath the car to allow the switch not to randomly open up when it shouldn,t usually set 1.5''below the floor...also had to replace the Valve stem o-rings on the maxton valve on all 4 solenoid posts..car would leak down if it sat idle and relevel.. problem went away and never came back good luck..

I'VE got a better one. My dlfb is coming in when the car is on the top floor. All hoistway and door lock contacts have been replaced. The issue is so intermittent it doesn't happen when I'm there. I've been told that the doors suddenly open then close then the car times out. So I checked all stop switches and finals. Still nothing.

Sounds like you are losing the feed to the DL valve. I would check L3S contacts. If they are good check the I/O board wiring. If you don't find anything replace the board.

According to my fault sheet a door lock that is bouncing can cause the same thing.

I chased this one for awhile. Tweaked the down side of valve never shutdown again????