I am assuming you mean you are getting an average of .440 v.
[ o2 is cycling ?]
With warm eng. and o2 sens. unplugged, take a sens reading when you unplug and cap the vac line to the fuel regulator.
[ sens should go rich 1v.]
Then, uncap the vac line [leave open to outside air], sens will go lean .1v.]
Also check ohms on sens heater to ground [although the heater
is in spec.] May have tripped #6 with an open circuit when hot.