02 sensor (bank 1 / sensor 2)

i have a 97 s10 blazer with a 4.3 vortec. i pulled the codes and came up with (P0140 - 02 circut no activity detected (bank 1 / sensor 2) i have 4 02 sensors on the truck, one on each side of the Y-pipe just after the manifolds, one just before the cat and one just after the cat. i called GM but they WOULDN'T tell me which one it was, but if i wanted to bring in the truck they would fix it, phone call after phone call, 2 days on the net, and i still not sure of which one it is. can someone PLEASE tell me if it is the one on the right, or left, or the one before the cat, or the one after the cat. thanks for taking the time to read this.

and why would my "check engine" light start flashing

Sensor 2 usually indicates the O2 after the cat. It would be very easy to monitor O2 activity with a scan tool. Once the O2 failure is recognized the suspected O2 can be uplugged to see if the values change in the scan data. If they do you have the right one, If they don't you have the wrong one.

Bank 1 refers to the left side of the engine on most chevy engine,( the side the # 1 cyclinder is on), sensor 2 is the post, after, cat sensor.

Your check engine light is flashing because the PCM is recognizing a problem that can potentially harm the catalytic converter.

Bank 1 refers to the left side of the engine on most chevy engine,( the side the # 1 cyclinder is on), sensor 2 is the post, after, cat sensor.

ok if Bank 1 refers to the left side of the engine, and sensor 2 is telling me it's AFTER the cat, why is Bank 1 even be there when i only have one 02 sensor after the cat, and the cat runs down the right side of the truck. i can under stand the sensor 2 cause it's telling me it's after the cat and i only i sensor after the cat, but the Bank 1 makes on sence. at $100.00 a pop. i dont want to be wrong with the sensor. i've read some stuff about the two sensors just before and after the cat, and it seems that the two sensor at the front on the y-pipe does all the work and the two sensor by the cat wont afect the performance of the truck. i know you cant believe every thing on the net but boy am i confussed.

this truck is going to be the death of me yet. prior post i put here today was for code P0140 - trying to find the right 02 sensor. but something new has happened, i took the truck to the store, and on the way back it seem to shut down for a split second (lights came on the dash, and all the gauges dropped, and no throttle respond), and this happened 4 times in about 2 min. i have no clue what caused this to happen.

I just had a great idea! Doesn't happen to often but when it does its usually a why didn't I think of that.

Unplug the one you think it is and drive it around the block. It should trigger another code for missing voltage. If the new code is for the same O2 that the original code was for than you found your O2.

See, your thinking to yourself Why didn't I think of that, aren't you!! :grinno::naughty:

I just had a great idea! Doesn't happen to often but when it does its usually a why didn't I think of that.

Unplug the one you think it is and drive it around the block. It should trigger another code for missing voltage. If the new code is for the same O2 that the original code was for than you found your O2.

See, your thinking to yourself Why didn't I think of that, aren't you!! :grinno::naughty:

ok your right!!! WHY DIDN'T I THINK OF THAT?
so i did it and got the locations of ALL the 02 senors
i'm putting in in a new thread if you want to see it
thanks again, but boy do i feel STUPID for not thinking of it.

With 4 sensors Bank 1 sensor 2 is between cat and engine right in front of cat.

But 02 sensor codes do not say replace sensor but check it out.

A flashing check engine light can be as said a cat waring or can also be a missfire warning.

On the truck shutting down you have more problems than 02 sensor.
A 97 is a bad year for ign switchs going bad.
Check that out real good first thing.
How many miles on it?
Has switch ever been replaced?

It is best to stay with the post you started instead of making new post/Thread.

ok thanks for the info on the truck shutting down, but were would i find the ign. switches, and how would i check them.

ok thanks for the info on the truck shutting down, but were would i find the ign. switches, and how would i check them.

Run a search in how to on ign switch.
And
Get some good repair info.
Factory repair manual or a all data online sub.
http://www.alldata.com/products/diy/index.html