a car was brought over for me to hook datamaster up on
and i noticed that the o2 sensor voltage went to .453 mv
on start up and never changed on a 20 minute drive . i know that it
should swing on either side of .500mv fairly rapidly as the
ecm modifies the pulse width of the injectors . i had no
error codes on the car concerning o2 sensors . any idea
why neither o2 sensor was sending a reading to the ecm ?

 

Check the wiring and/or replace them.