I'm at a loss and couldn't find anything online so hoping to get some help here.

I have a 91 n/a 2+2, I just recently replaced both O2 sensors and the passenger side (battery side) sensor is not working and the car runs like its in limp mode or something(bad/hesitant acceleration, loss of power and rough idle. I checked the harness side of the O2 sensor to confirm I am getting 12 volts. I checked the resistance of both new O2 sensors and they both (the functioning and non functioning O2) read about 8.8 ohms. I can see on ECU talk the passenger side O2 sensor stays on 1 (rich?) and the volt reading doesn't change. While the working O2 switches as it should 0-1 and changing volt readings to match. I also did an ecu reset by turning the pin on the computer.

new O2 sensors are bosch 13091

Any ideas why the new O2 sensor isnt working?

huge thanks in advance

It may just be bad out of the box, its not unheard of. You may want to try swapping the sensors and see if the result follows.

NolimitZ32 wrote: ↑

Thu Jun 04, 2020 5:06 am

It may just be bad out of the box, its not unheard of. You may want to try swapping the sensors and see if the result follows.

With the sensor resistance being the same as the working o2 wouldn’t that mean the sensor is in working order?

Not necessarily, the zirconia element reacts to chemical changes in the environment (presence of oxygen in the exhaust gas) which causes the voltage produced by the element's chemical reaction to fluctuate. If the element or any components internal to the sensor aren't right in some way then the voltage will not be produced or be produced incorrectly (won't fluctuate) in response to the gas and will keep showing a constant voltage or some voltage which the ECU doesn't understand thus producing unwanted results.

ok thanks i'll give that a try

Beyond that the sensor circuit at the ECU could be bad or the sensor wire somewhere in the loom could be damaged. You would need to probe at the ECU harness to see what the sensor is putting out.

so after some more testing I got the Passenger side O2 sensor to work. The problem is the driver side O2 switches from lean to rich reving at 2-3k rpm while the passenger side O2 doesnt start switching from lean to rich unless reved to 5k or more rpms. Any idea why they both are not working at the same rev ranges??