I just pulled my downstream O2 sensors and plan to pull the upstream once I get to the connectors, but how can you tell if an O2 sensor is bad? My downstream sensors usually run at .015 volts and the upstream run at .970 or .990 volts, although I have seen the S1B1 go as low as .550 a time or two. I am getting 10 MPG or less and have read that bad O2 sensors can cause poor gas mileage, but how do you know if the sensors are the cause. I've also read that you should not try to check resistance or you can damage the sensor, so I have not.

The downstream sensors are stamped 73J6 on one flat of the hex and SAGEM 04LS001 and NTK JAPAN 4LS on the upper body and they have gray 4 wire connectors on 18 inch leads, so I assume they could be OEM sensors with 171,500 miles on them but I have no service records to know if they are newer. Some sources say to change them every 60K miles and some say heated sensors are good for 100K miles. Mine show no particular build up or odd colors on the working ends.

I believe I read someone suggested soaking sensors in brake cleaner overnight to clean them and I assume you would soak just the working ends and not the whole body. Anyone have a better suggestion or a better cleaner?

I am thinking of swapping my upstream and downstream O2 sensors to see if they read the same values I have seen before. I also read that if the upstream sensors are cross connected you will get poor gas mileage and codes; anyone know how to identify left and right connectors so they are plugged correctly? Or is it obvious once I get to them?

I am checking the sensors because of repeated P1314 and P1313 codes and a flashing CEL, especially with a cold engine, but I hesitate to just throw $400 worth of new sensors at if these may still be OK.

PS: I cleaned the outside bodies of these downstream sensors with brake cleaner and a hand wire brush - I did not clean the tips other than wiping them off with a paper towel.

 

ok first off the downstream on this only say the cat is working so i would not bother with replacing em unless you are getting a code for the sensor bad

second, the upsteams at idle watch values they should rapidly fluxuate

third these suck on gas lol

and forth , best price i found was amazon for ntk

iirc antifreeze will kill these like if you had bad hg before


as far as cleaning em theres probly a thousand backyard ideas not sure any work, maybe just give a false sense of accomplishment lol

 

You can watch your O2's with an app like Torque.

 

Pretty cool graphs, although the values look pretty high (rich?) on them. Is that a smartphone app or a device? I am tracking my O2 sensors on an Ultragage Plus which gives current values as they change - I'll have to check to see if it can graph, but I don't think it can. I also have an Actron code reader that may be able to do graphs, perhaps one sensor at a time.

Still thinking I'll swap downstream and upstream if I can get the upstream out, and still looking for that post on cleaning them.

 

I'm not sure you should waste your time attempting to even clean these things especially if you're working on the originals as a lot of the times they just go bad through wear and tear and it's not entirely a dirt problem. Plus changing the upstream sensors was a PITA (at least for me) and I would only want to do that once.