o2 Sensor replacement diagnosis
 

P0139 o2 sensor circuit slow response bank 1 sector 2


So I guess the downstream oxygen sensor circuit needs to be replaced, will this be good enough:

http://www.ebay.com/itm/234-4613-Oxy...BYYd69&vxp=mtr

It's for a 05 civic LX
Reading my manual I'm not sure what exactly to do, though I found a video
this seems like the correct process, but I want to be sure.

Also, is it possible that it has something to do with the fuel injectors, or a poor electrical connection or something and how would I diagnose that? Don't want to waste money on a sensor only for that not to be it.

Also, how long can I drive it with a slow sensor I might not be able to fix it for a month. Thanks.

Re: o2 Sensor replacement diagnosis
 

From my observations, the 7thgen ecu can be rather finicky when it comes to o2 sensors. Maybe someone else can chime in If an eBay special sensor will play nice

Re: o2 Sensor replacement diagnosis
 

Yes the code is for the rear O2 sensor.


Problem #1: The video is for an EX, it's quite different from the version of the car you have. If you peep under your car you should find your exhaust doesn't look anything like the one in the video.

Problem #2: Cheap parts are rarely a bargain.
I strongly recommend using the same brand of sensor the factory used. It was originally equipped with either Denso or NTK brand.
I'd remove the bad one, verify the brand name on it, then visit the website of that manufacturer to get a part number, then check local parts stores for the same number in the correct brand.

A little google says NTK was the original brand.....and their catalog says sensor #24243 should be the correct OEM part for your car, direct fit, correct connector and all that.

If it happens to be a Denso brand, 234-4092 should be the part number.


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Your engine compartment should look like this one pictured below (google pic).
You can find the primary sensor right in front.
Secondary sensor is at the bottom of the manifold below the catalytic converter..... You see the two sensor connectors to the side (labeled), just follow the wire to the sensor located down low.
You will need to be under the car with appropriate tools to remove it.

http://i68.tinypic.com/2yjo3dj.jpg

Re: o2 Sensor replacement diagnosis
 

thanks for the detailed response, do you know if I can leave it unchecked for roughly a month? Or is this something I should do asap.

Re: o2 Sensor replacement diagnosis
 

Well.....if the CEL is already on, you might not know if new problems crop up unless the engine explodes?

I don't think waiting will hurt anything though. JMO

Re: o2 Sensor replacement diagnosis
 

Theoretically, it'll just make it so the ECU is erroneously reading catalyst efficiency. Shouldn't hurt anything operationally. Like ezone said, you won't know if there's another CEL that pops up unless something actually happens (well, without periodically checking for codes other than the aforementioned P0139 code)

Re: o2 Sensor replacement diagnosis
 

So the downstream/rear sensor is the Secondary o2 seen in the picture. Can I just open the hood, unplug and look at the serial on it if there is one? Do I have to jack it up and look under to find the brand?

Also as for the socket to remove it, I was thinking of getting this one:

but there's one like this:

do you know from experience which is easiest to work with? the normal socket one seems more intuitive especially for torquing it to spec.

Re: o2 Sensor replacement diagnosis
 

Alright I looked at it, couldn't see any serials, both of them have blue wires
Looks like this from amazon the NTK #24243
https://images-na.ssl-images-amazon....L._SL1500_.jpg

The Denso looks like this:
https://images-na.ssl-images-amazon....1HWRKUQnNL.jpg

Would it hurt to just buy the NTK since that's what it seems to be or should I make sure?

Also... is it possible it's the connector that you attach the o2 sensor too, and not the sensor itself? Or would that be a different code than P0139

Re: o2 Sensor replacement diagnosis
 

I have a variety of sensor removal tools. I can't tell you which one will work best for your application.
Also, Check if the parts store will loan you the tool(s) so you don't have to buy them.




I'd go ahead and get the NTK part. It looks like (your pic) it even comes with the correct rubber pads in the middle of the wires to fit into the holders on the car. (surely you saw those holders while you were under it)

You'd have to remove the sensor and look closely at the shell for the name, or use a wire wheel to get the corrosion off so the name can be read on the steel if it's there.

Pic here is of a pair of sensors removed, one I held to a wire wheel to clean the rust off and expose the brand name on the ring above the hex
Attachment 113684