Replacement Interval for 2.4L O2 and AF Sensors?

I have the 2003 2.4L Tacoma with 73,000 miles.

Are the Oxygen and Air to Fuel Sensors supposed to be replaced at any particular interval, or do you just wait for a Check Engine code to alert you that one has failed?

 

Just wait. MAFs have lasted for a long time with no consumables in them. O2 sensors do need to be replaced. Most wait for the MIL since they are not cheap.

 

I'm not talking about the MAF....by AF I'm referring to what some people call the "upstream" O2 Sensor. As I understand it, there's an upstream O2 sensor (actually an Air to Fuel sensor) BEFORE the catalytic converter and an actual O2 sensor AFTER the converter. Just wondering if these two sensors should be replaced at a certain interval.

I think you're right about the MAF not needing regular replacement, though. I have a feeling those are VERY expensive.