[2006mazda3]

i am attempting to fix my CEL on my 2006 Mazda3. the code is a "Stuck lean" on the downstream O2 sensor. replaced the sensor and it didn't go away. I started looking at the actual voltage put out by the sensor, flat line at zero volts. I swapped upstream and downstream sensors and still got exactly zero volts on the downstream sensor. so I am thinking there is a wiring problem between the sensor plug and the computer and idea how I go about tracking it down or bypassing it by putting new wires in altogether?
thanks a bunch

Given the age of the car I wouldn't particularly care about this issue, but I need to pass NJ inspection

 

[kms1990]

there should be a fuse for the o2 sensors, find the one for the rear and check it before assuming wiring as the old sensor may have shorted internally and raised the resistance of the circuit too high for the fuse and blew the fuse