So I recently swapped a new motor in my 1990 Na. I found that both my O2 sensors were bad, so I installed new ones. When I put the car into diagnostic mode to test the O2 sensors, I get a reading off the passenger side sensor but not the drivers side. I have swapped the two sensors and the same thing happens, only the passenger side reads. I have changed the connector on the harness side for the O2 (it was pretty bad) and have done a continuity test of the wires going back to the main ecu connector. There is also power to the O2 sensor so it seems as though the ecu isn't reading the signal from the O2.

My question is, is it possible that when the connectors for the O2 sensor and coil #5 get swapped it can cause damage to the ecu?

I did make this mistake in the beginning but have corrected the issue now. The car does not misfire but it does hesitate, and I believe that's due to the lack of input from the O2 sensor causing the car to run on closed loop parameters.

Have you checked continuity to ground on the ground pin?

I have continuity back to pin 115 at the ecu which is "O2 sensor ground".

At face value it all points to the sensor circuit being damaged either in the harness or the ECU. Do you have an oscilloscope available? If so check the signal with the car running at the sensor and at the ECU pin by backprobing. If you don't have a oscilloscope you may be able to get a good DMM with a fast enough refresh to show you some movement though it wont be anything you can really make sense of. Other option is to try a known good ECU, try to source one locally. Id let you borrow one but the last guy that I let borrow my extra ECU never returned it and ghosted me.

I've been trying to locate one locally for a couple days with no luck. I don't have access to an oscilloscope unfortunately. I did have that idea, but didn't realize I might need one of those to do the test. Maybe I'll try it will a meter anyways asnd see what happens