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Replacing your primary O2 sensor

67K views 25 replies 9 participants last post by  del.ray.sol 
#1 ·
I recently had an O2 sensor go bad. I did this little write up to help out others who may need to replace theirs. This was performed on a 2000 Honda Civic DX.

Upon learning that your O2 sensor is bad, here is what you will need:

Autozone (or some other auto parts store) will have your O2 sensor. Hopefully it will be BOSCH. Once you get your new O2 sensor, also pick up an O2 sensor socket. This $10 tool makes it MUCH easier.

Tools needed:
Ratchet with 10in or more extension
O2 sensor socket
10mm socket
vice grips (or similar)
good heat resistant gloves


First, you will need to make sure the engine is hot. Not terribly hot, but run it for a few minutes before you start, it will make the exhaust manifold expand due to the heat and make replacement easier. Once the engine is hot, unplug the O2 sensor from the little metal tab it is anchored to, then unplug it from the wiring harness. BE CAREFUL all hoses and metal object will be hot! Remove your heat shield by taking off the 2 10mm bolts that hold it on. Then slide it off the pigtail harness od the O2 sensor. Then slip your O2 sensor socket over the O2 sensor. It is just a big 23mm socket with a large slot in it to feed the harness thru. Then slide your socket extension between the two rubber hoses routed along the radiator support, then attach your ratchet. Turn it until the O2 sensor is ALL THE WAY out. Then carefully remove the tool. pick up the O2 sensor by the harness; IT WILL BE VERY HOT! Then take your new O2 sensor and place it into the socket. Hold the harness carefully so it does not get twisted as you tighten the O2 sensor into place. DO NOT OVER TIGHTEN!! There should be anti-seize on the threads to aid in installation/ future removal. Then route the harness thru the hole in the heat shield and bolt up the heat shield. The bracket on the front left portion of the motor will not hold the O2 sensor wire in place due to the new one having no rubber plug on it. Put the wires into the little U and then close it up slightly with the vice grips, but not so tight you squeeze the wires. Then re plug the harness to the car, and attach the plugs to the metal tab again. All you have to do now is Reset your ECU and you are good to go.
 
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#3 ·
not a bad write up...the way i do it is usually take the bottom piece of the header off...unplug the o2 sensor, put part of the header in a bench vise and then take a regular adjustable wrench, or open ended wrench and just pull like hell until it turns...but whatever works, if you are slick enough and your car isnt super low you might even be able to do this while its on the ground
 
#4 ·
for an EX its a little different as well...

the angle of the O2 sensor and the fan shroud kind of limit your way of removing the sensor.

you (at least i had to) remove the primaries first, then remove the sensor. between the sensor and the fan shroud there wasn't enough room for the O2 socket and the ratchet to be anywhere near getting the sensor out. even i had somehow managed to get them both together and on the sensor, there wasn't enough room for me to actually turn the ratchet or unscrew the sensor all the way.

also, this was on a 96-00, the 92-95's may be different by some margin.
 
#5 ·
ho2 replacement isn't difficult, but this is a serious situation I am trying to solved it:
I have a 98 hatchbk and I am having a problem with the emission. I swapped a 96 Ls motor into a 98 chassic. The stock DX harness has been replace with OB2 Ls harness. Everything is running in excellant condition, but I have a situation with the secondry ho2 sensor. I can't seem to located the plug from harness. I am not sure if the plugged for the secondry ho2 is on the motor or on the harness. It looks like there is another wire that runs from the main harness supposely connecting the plug of the ho2 sensor that I may be missing. (NOT TOO POSTIVE ABOUT IT) I been having this problem for 3 mo. Please help me config. this emission problem.

ANY CLUES???
 
#6 ·
What about the o2 sensors on a b16a CRX SiR engine, what USDM o2 sensors can replace these? Theres two and they are side by side, I need to know what can replace these or if there is some kind of alternative like getting a header with a single o2 sensor or something, I have no knowledge about this and I need my o2 sensor thing figured by next year. Do I even need to have both o2 sensors or is that just there for Japan emissions? Could I get a USDM b16a header and just use one o2 sensor setup and be okay for emissions? Help please. Btw engine is in an 89 Civic DX hatch.
 
#7 ·
i have a small problem with mine.

as i was driving my 95 nissan 200SX i heard a sound like a rock hittin metal. but i didnt see any rocks on the road, it was almost perfect. but i didnt pay much mind. i got to a red light and waited for it to turn green. when it did i pushed down on the pedal and noticed the sound of my exhaust was coming out like a fart can. but it was only on low RPMs. so i did wat i had to do and came back home. on the way back i heard another bang noise and the sound got a lil bit fartier. i looked under my car and noticed my O2 sensor was hanging there. so i drove the car on the little drive on ramp and tried to get under it. i'll try to get pics of what i saw. but basically it was forced off somehow and now theres a hole in the spot where it goes on. so i guess some welding will be involved.

so any suggestions, questions, comments, and help would b greatly appreciated
 
#9 ·
it should thread in like a bolt. if the bung welds came off, you'll have to have it re-welded, for sure. but don't weld the sensor in.
 
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#11 ·
Hoody Racer said:
well yea i wasnt planning on welding the sensor on. i was thinking about welding like a bolt there. because as u can see its just a hole, nothing to thread into
yea, you posted those pics right before i posted, didn't know they were there..
 
#12 ·
did your o2 sensor break off in the cat? that's what it looks like.

you'll need a new sensor, and an o2 bung, which is pretty much just a nut. you can get them online for cheap, like $.50
 
#17 ·
Hoody Racer said:
well it LOOKS good, but it has some rust on the threads. but im sure that can come off.
couldn't tell if the tip and threads were still there or not. they don't take too well to abuse, but there's only one way to find out if it will still work or not, and that's see if it throws a code.
 
#23 ·
Ok. I'm about to replace the 02 Sensor on my 95 Honda Del Sol Si, bc the check engine light just came on and it pulled an 02 Sensor code. The question I had was how to tell which 02 Sensor needed to be replaced? The code doesn't tell you that info, but I'm sure there's some diag steps. I have a multi-meter. Any suggestions, or anyone want to write a quick writeup?

Thanks,
--A

:ninja Ninjas are all around me. :ninja
 
#25 ·
Ok... So the scoop. I tried relentlessly to get it out. I tried all of the suggestions above. After accepting my defeat, I took it to a mechanic. He couldn't get it out.

FUCKKKKKKKKK! (go ahead SH and mod my post. I'm just pissed)

Ok. Solution. I found a header two hrs away on Cragslist. I'm gonna go up there, but the $40 header, drop my new 02 sensor in it (if the one in it isn't already good) and Wala. Done.
 
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