hey...i have a 1998 chevy s10 blazer v6 with the vortec (i think thats how its spelled) engine...where are the O2 sensors located? they need to be replaced and i haven't a clue where to locate them to know how many i need and such...

 

If its the same as a 97 there are three one on each head near to the cat and one after the cat. What makes you think they all need to be changed, they arent cheap and rarely fail together?

 

had a diagnostic run on the truck because check engine light came on and it was feeling as though it would stall and it said 1 O2 sensor was bad but to be safe i am changing all 3...

 

also i found a place that i can buy all 3 for 125.00 including the shipping so its not too bad

 

Ok, back away from the truck and start with what you are experiencing. What code was stored in the PCM?

There is absolutely no need to replace all three sensors unless you like money flowing out of your wallet for no real reason.

As far as locations go, there is one on the driver side down pipe directly after the connection between the y-pipe and the exhaust manifold on the engine. This is the B1S1 sensor. The B2S1 sensor is located on the passenger side down pipe between the passenger exhaust manifold and the "Y" in the y-pipe. Then your third sensor is located after the catalytic converter. This is the B1S2 or possibly B1S3 (depending on the programming of the PCM). B1 == Bank 1 (driver side). B2 == Bank 2 (passenger side). S1 == Sensor 1 which will always be the upstream sensor. S1 sensors are the only ones which affect the operation of the engine. The S2/S3 sensors are emissions monitoring sensors only.

One other word of advice. Do not get anything but AC Delco O2 sensors for your truck unless you want to be replacing them again shortly. Sure you could spend $125 for all three sensors, replacing two sensors for nothing only to have to replace them in a much shorter time frame. The AC Delco AFS105 (OE#25312200 or 19178918) is the proper sensor for all three locations on your truck.

 

If those sensors are bosch you better keep the ones you take out because you will be putting them back in a few months. Also you should look at the sensors before buying them there is a chance that the wires melted causing the sensor to report to the pcm wrong.

 

How difficult is it to do this on a 2001 4X4 Blazer.....Bank 1 Sensor 2 ......This is the "middle" one right after the cat....thanks !

 

Easy. Just get yourself the appropriate wrench, disconnect the electrical connection, and remove it.

And yes, it is the post cat sensor.