I have a Bryant 350MAV048100 furnace. It runs for 15 minutes, cycles off and then cycles on and shows an error code 31. I've cleaned out the intake /exhaust lines, but still have the problem.

Did you try cleaning the drain? The fault codes should be listed on the back of the door.

Find codes here, page 15. Follow table to check possibilities. 31 = pressure switch did not close or re-opened.

I have a Bryant 90 Plus 350 MAV and it recently started not completing the heating cycle. It would shut down premature with an error code 31, but then would turn back on in a few hours. Reading this post caused me to check my drain lines and there I found water was backed up due to the collection box being clogged from 13 years of neglect. Seems like cleaning it did the trick, the tempature, as well as the looks I was getting from the wifey are both much WARMER!

Thanks Guys!