Question on BMW 3-Series E36 O2_Sensor

I changed both right and left #1 oxygen sensors before cat converter. I still get engine light after it warms up. Runs fine cold and then bang it gives engine light and starts running ruff. I put tester for codes and it still says #1 oxygen sensor and now it says #2 oxygen sensor is bad. Could the #2 be bad and causing a fault code on the #1 that I already changed? Possibly a bad new sensor? I am looking on where the #2 is located after the cat and how many sensors. Would you know this and how many #2 sensors their are?



I also cleaned all the electical connectors I could find in the engine compartment and on the sensor connectors.



Thank you for any answers.


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[Nick at Pelican Parts]

If your vehicle has 4 oxygen sensors, two will be before the cat, likely in the manifol and 2 will be right after the cat in the exhaust pipe. The code may not denote a faulty sensor but instead something else that is causing a fuel control issue. I would double check the code and go from there.

- Nick