Can someone tell me how many O2 sensors I have to replace and where they are???

 

Been covered before and I have posted this image depicting the oxygen sensor locations in a few different posts:


What is happening that you are considering changing the O2 sensor(s)? If you are doing a general tune up, only the B1S1 & B2S1 sensors should be considered for changing as the B1S3 (post-cat) is an emissions monitoring device only and should only be changed if a code specifically stating a problem with that sensor and all diagnostic procedures have been completed resulting in the conclusion that the sensor is in fact at fault.

 

I purchased my Blazer back 1n 2006 @ 96,000, and here I am about to hit 130,000. My LS says that I'm getting 14.4 mpg and I am about to do as complete of a tune up is possible before I start adding all the mods I want ie. AEM CAI, Gibson Exhaust, JET ECM programmer, CFM-Tech Ported Throttle Body and JBA headers.

 

So the O2 Sensor labled as #1 in the diagram does not need to be changed unless it codes???

 

Isn't that what I said...? It has nothing to do with engine fuel management.

 

I wa just confirming thanks.