yet another topic about oxygen sensors

[robcarync]

alright...i got a new oxygen sensor because my check engine light code says it is bad. now from what i understand....there are TWO oxygen sensors...how can i tell which one is causing the malfunction? is there anyway to know for sure which is the bad one?

and me and my pops are going to be working on this project tomorrow...so if anyone could give me a description of approximately where they are located...thatd be great!

from other threads...the front one is under the front and you have to get under the car to get to it. is it drivers side or passenger side or middle...is it close to the ground or farther up?

and the back one...how to find that one.

from what i understand you just unscrew them and screw in the new one. i got the oxygen sensor tool and all that so i guess i just need to know where they are located and how to figure out which one is malfunctioning.

[ClubSport]

They are both under the car. One's in front of the catalytic converter, one's behind it. This is only if you have a 1996 or later car. The '95s only have 1 sensor. They'll be easy to spot as they are the only things with wires coming out of them that are screwed into your exhaust pipe. They are usually siezed on there pretty good. You'll just have to use the process of elimination to find the bad one, if the code doesn't tell you which one is bad. Most cars do.

[robcarync]

ok well i have a 95 ti...so looks like i only have one to worry about! thats a releif because i just read somewhere that Ti's have 2, and m3s have 4...

i was just worried cuase i didnt know how to find the bad one...god thing there is only one to worry about.

yeah i read about oxygen sensors being tough to remove cause they are screwed in there really tight...thats why my dad suggested to buy the tool as well...hopefully make things a bit easier.

thanks for the info!

[robcarync]

ive now found the o2 sensor. my dad took my little brother and his friend to the movies so im left here to attempt this on my own. ive read several online instructions for doing this so i think i should be good. right now im waiting for the car to cool off because my dad drove it this morning...i made the mistake of accidentaly touching the exhaust pipe while i was under the car and well it burned.

so from what i understand you just unplug, unscrew, then screw and plug the new one in.

does it have to be done in that order? thats the order i read from J!M in another thread so im gonna do that...i dont know if the order matters...but id hate for it to be like the battery and sparks go flying if i undo the wrong end first.

and one more ?

do you have to unhook the negative battery cable...i read in one tutorial that you should...but the three others i read didnt mention it? i dont think itd matter but i figured id just check.

[bimmerboi318]

i'd stick with that order of unplug, unscrew, screw in, plug in...because if you try to unscrew it with it still plugged in, it will twist up the wire. thats the only reason i can think of. as far as the battery, it might be a good idea to unhook it...but the biggest thing to do is make sure the key is OFF. these are heated O2 sensors and when the key is switched on the sensors heat themselves to well over 1000 degrees (i believe). the reason they do this is because they have to be hot to work, and they can work sooner like this if they dont have to wait for the exhaust temp to get hot. so, make sure those keys are in your pocket or something.

you should be able to use a regular open end wrench since the sensor is in a relatively easy spot to get at. although i've never taken mine out, so i cant be 100% sure. and when tightening the new one, i usually just treat it like a spark plug as far as how tight to make it.

[robcarync]

im done. i got it changed all good.

i noticed the same reason to do it in that order too...because it twists up the wire.

thats an interesting tidbit about the o2 sensors being self heated...and i did have the keys not on...they were in the cup holder in the console. good thing.

i didnt bother unhooking my battery though.

my dad also purchased the o2 sensor tool from bavauto so that made things easier...although that beast was in there tight...i had to get a rubber hammer and knock the socket wrench a few times to get it unstuck.

but overall, all went well.

it was kinda tough because i had no jack stands ... so i ended up making a really ghetto contraption out of 2x4's and some 2" steel tubing i had in the garage...probably unsafe but luckily the car didnt crush me.

[bimmerboi318]

i highly suggest buying a set of 2, or even 4, jackstands. they're really a must if you are working under your car. they're not that expensive either. worth every penny. glad to hear it worked out though.

[robcarync]

haha yes i know jackstands are in the purchasing process...i walked outside and my dad was like "yeah we dont have any jack stands right now..."

im pretty sure we had some laying around our garage somewhere but id dunno what happened to them...but we'll be getting some next weekend