Light comes on and scanner (AutoXray 5000) says downstream O2 sensor. Scan of all O2 sensors signals show two upstream and other downstream moving around as they should but the bank 2 sensor 2 reads zero. Quick trip to store for new sensor and still zero.

any ideas?

 

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P0156 O2 Sensor circuit malfunction bank 2 sensor 2

connector unpluged and replugedwhen install new sensor installed

MIL elims on truck due to awol exhaust parts

 

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downstream sensors have 300,000 miles on them and only cost $30 for Bosch. with the ease to change them, low cost and high miles it was the logical first step. especially given the low teens temp and ice in the drive way. in warmer weather i prob would have swapped sides to see if code moved.

 

Logically, if you interpret the code correctly, it tells you 'circuit' malfunction, not that the sensor is faulty.
If a Scanner tells you the output is zero, the circuit cannot pass any signal from the sensor or; the computer has abandon it because there is no usefulness to the signal if the cat system is faulty.
Replacing the sensor on it's open circuit does not fix the problem.
If the cat is faulty, the system can abandon the reading because it has no usefulness being out of limits and setting a code..
Your working with a computer system so there is no guessing or hoping.
Luck would be the better of those two.
Find and repair the open circuit.
The sensor 'generates' a voltage from heat and oxygen sensing so there is no 'continuity monitoring' involved to tell you the sensor is faulty on 'that' basis.
Good luck.

 

bad original O2 sensor, defective replacement, works now. luck of the draw for bad new parts. thanks to all for helping me think it thru