Maytag neptune washer flashing a symbol uF - Maytag Neptune MAH6500A Front Load Washer

SOURCE: maytag neptune tl

Code OP means lid is open. If it really isn't, then the problem is with the switch that sense whether the lid is shut or not. Could be bad switch or bad connection.

SOURCE: maytag neptune washer display showing FL

fl is a over fill. clean the pump out and the sump near the pump is in the back the dran hose goes to it

SOURCE: My maytag neptune Model #: MAH5500BWW is flashing

The error code you describe is not listed in Maytag's book of codes. The link below will take you to Maytag's website error code page where you might be able to match it up.
http://maytag.custhelp.com/app/answers/detail/a_id/2885/session/L3NpZC8yY3lEMjNEag==/sno/0

SOURCE: Maytag Neptune washer has bad odor, city water.

There is no filter in your washer that would cover the odor issue.
The website link below will give you all the information concerning odors in a Maytag Washer

http://maytag.custhelp.com/app/answers/list/kw/odors/p/293/r_id/108284/sno/1/search/1/session/L3NpZC9RRDdZdDhEag==

SOURCE: my maytag neptune washer smells musty. what is

I owned a maytag neptune washer and had to run dishwashing liquid thru it occasionally to get the smell to go away. Finally we learned about a new gasket retrofit that they were doing which was covered by the maytag company we called and they installed it for free and the smell stopped. I had that washer for about 10 years and probably spent as much fixing it over the years as it cost. I now have a whirlpool duet front loader and love it. no smell and not problems. Try the electric dish washer soap.