my check engine light has been on for awhile now, and my codes coming up as an oxygen sensor. bank 1 sensor2. the problem is, noone can tell me what sensor that is. My autoshop teacher said that on GM's bank 1 is the odd side cylinders(1,3,5) and bank 2 is the even ones. So he thinks its the one after the cat, cause its sensor 2, even tho theres only one after the cat, and its more on the passenger side. Can anyone verify which sensor this is? Thanks

 

Sensor 2 is behind the cat. There's only 3 sensors on these blazers (at least any that i've seen) b1s1, b1s2, b2s1. Sensor 1 would be the ones closest to the manifolds reading the fuel mixture, sensor 2 is the one that measures catalyst efficiency.

 

Thanks. I was pretty sure it was after the cat, but when i went to autozone i told him it was bank 1 sensor 2 and hes like thats before the cat, so it had me questioning myself. I ended up not even getting it cause they only have bosch ones, and I wanna stick with AC Delco or Delphi

 

so would this indicate that possibly my cat is bad? Or just the sensor went bad? if its my cat, ill guess ill go with a high flow magnaflow cat. whats the chances a cat went bad at 50k miles tho?

 

Most of the time you can drill them out and that will make it go off the cat. im talkin about haha.

 

Ehh id replace the sensor before you go about a bad cat.

 

if the sensor doesnt do anything to engine perfomance tho i really dont wanna replace it. If i just do the spark plug antifouler thing to the post cat o2 sensor will that possibly make my light go off? I rather spend 4 bucks opposed to 80 for a acdelco sensor

i think it may be the cat cuz im getting 8mpg.. i doubt a bad sensor is causing that, especially the precat one which has nothing to do with performance. I dont think im throwing the code for a bad cat tho. Should I just replace it with a high flow cat? I can remove the old one and weld on a new one. Or should I remove the cat thats on currently and try to blow it out? Maybe its just clogged? Im not getting any rattles or anything. Just a SEL and terrible gas mileage. And it hesitates occasionaly

 

If it runs up to near red-line under hard acceleration, then the catalytic converter is not clogged, but you can do a back pressure test to check. An alternative to the back pressure test is a temperature test before and after the cat. The temps should be rather uniform at the inlet & outlet. If there is a large differential (hotter at the inlet then the outlet), then that is an indication of a restriction in the cat.

All three (two upstream, one downstream) of your sensors are the same. To check the sensor, just swap it with one of the upstream sensors. If the code changes to the new location, then you know the sensor is bad. For a post-cat sensor, it likely doesn't matter what brand of sensor you use since they do not switch at all.

 

yea, under hard acceleration it reaches redline. after talking to my auto teacher he said if my cat was clogged i would loose power so i know thats not a possibility. This sensor has nothing to do with gas mileage right? I would still like to know why i get such bad gas mileage. it runs strong and smooth. Distributor recently was replaced, as well as fuel filter, fuel pump, and air filter. It seems like after that work got done my gas mileage got noticeably worse. I havent really checked but i think im only getting like 175ish miles to a tank. Possibly time for some plugs and wires?