Hey guys I have a check engine light with the code p2a00.
Is this the driver or passenger mainstream? Also is there anything I should check before replacing the sensor?

 

Passenger side. Did you ever fix this? A year ago I had this code and replaced the sensor. That didn't help. A week ago I ended up taking it to a mechanic and he found a crack in the catalytic converter by doing a smoke test. It was replaced and I haven't had the code come back yet. The crack was located near the connection to the U-bracket that holds both cats underneath the car.

 

The passenger side (bank 1) A/F sensor is staying rich or lean longer than expected.

Possible causes:
• A/F sensor1
• A/F sensor 1 heater
• Heated oxygen sensor
• Fuel pressure
• Fuel injector
• Intake air leaks
• Exhaust gas leaks

Keep in mind the code is the SYMPTOM not the CAUSE. Sometimes they are the same, but not always.

Do you have a generic ODB scanner / ELM327 scanner?
If so you can look at your fuel trims and sensor 1 live data to figure out what the issue is.

If not, check for exhaust leaks from the exhaust manifold to past the rear O2 sensor.

 

Have a muffler shop check for exhaust leaks. I had the same code and after chasing and replacing approximately 10 different parts, it was a stupid crack on the exhaust system.

If the tech doesn't use a stethoscope while hunting the leak, go to another shop. After literally spending 4 months chasing this code and resetting the CEL every 50 mi, fixing the exhaust leak fixed it.