How long do O2 sensors last and how can you tell when to change them ?

 

By the book 100K miles- Alot of people would say 50K and most of the time you would not see a problem till it kicked a code.

 

I'd add that it probably depends on which sensor. I've gotten the code for the post-cat sensor on and off for months now. It seems to come in waves, with some months seeing several SES lights and others without any codes. Since there is no change in drivability, I've been advised to leave it alone.

 

O2 sensors gradually degrade over time. They usually don't go from perfectly working to perfectly broken overnight. The reading just gradually changes and gets off, so tells the motor to change the air/fuel mixture. It reads lower and lower voltage, which equates to thinking the motor is lean, and richens the mixture from where it should really be.

Eventually it gets to the limit and kicks a code. That might or might not be around 100K miles. The EPA says they should last at least 100K miles. It depends on contaminants and ash accumulation, and that'll vary a lot.

That's supposing everything else is in working order. If you have a fuel or ignition issue, the 02 sensor (and cat) can suffer pretty quickly.

Your mileage can get gradually worse, and you could save some money if the O2 sensor is getting far from "new".

Me? I wouldn't wait till 100K (or a code) unless I could test the sensor. If you had an alternate a/f ratio sensor (tail pipe one, etc), you could measure the O2 sensor's output, and see whether it's very far off.

 

so if the car has been raced and has a 19% pullie the O2 sensor might go bad faster ? Or its been tuned perfectly ,run hard and hot , and should last for 150K? Thank you for your time. PMF.