Replace O2 Sensor - DIY (for P0136)

I'm a new Gen 1 owner and have a 2002 which is regularly throwing a P0136 code. Mostly just this code but recently added a P0440. I've done a fair bit of research here and elsewhere and consensus is the downstream O2 sensor may be the culprit. Currentl at 170K miles and O2 sensors were replaced around 100K.

My self assessment of my mechanical skills is about 4/10. Is this something I should take on myself? Video looks straightforward but what worries me is many say this can be a more complex situation that may be more than just the O2 sensor. Maybe try the O2 sensor replacement and see if it turns out to be simple fix?

 

Just calculated that I am getting about 17.5 MPG in the city. This doesn't seem terrible?

 

Welcome to TW, as you see by the videos it's not a lot of work, your biggest challenge is likely going to be getting the bolts off due to rust. As in this video spray the PB Blaster on there a couple days in advance of doing the work. I had to use a dremel on the nuts of my '94 pickup when I did it and replace the nuts. A nut splitter would work but didn't have one and not sure if there's room to get one in there. Your MPG sounds in the range but I don't pay a lot of attention to MPG ("It is what it is.")

If they were changed at 100K I'd be suspicious it's something else, they generally last a long time.

 

You have two separate concerns with those codes

Do you have a live data reading scan tool? If you do we can help you diag it

 

@rocknbil The O2 sensors were replaced at 106K miles and I am now at 171K. Is 65K a reasonable time to replace again? Thanks for your earlier reply.

 

@joba27n I have a basic scan tool which is how I pulled the P0136. Showing my limited knowledge here but what is a live data reading? I recall something about that in the scan app but not sure it produced any data.

 

Did this job on a 1996 TACO 3.4L 4x4 automatic both front and back sensors. Purchased Denso oxygen sensors from RockAuto. Purchased tool below to R&R oxygen sensor.

As always it’s wise to replace with same like item to prevent possible code issues.

Multiple Utube videos on How To.

Don’t forget to place the packet paste on the threads of the new sensor to seal the connection, this paste packet should come with the new sensor.

Note: there are several types of tools available for this purpose and you may need a different design to access your sensor’s. Which suggest you see how much working room you have for this job before investing in any tools. Good luck

$11 DURATECH O2 Oxygen Sensor Socket 3/8" Drive x 7/8"(22mm), Oxygen Sensor Remover Tool Chrome-Vanadium Steel with Side Wire Gate, O2 Removal and Installation

https://www.amazon.com/gp/aw/d/B0CF8M9DJ3/?_encoding=UTF8&pd_rd_plhdr=t&aaxitk=69607cc544930ba31158a16c2014d648&hsa_cr_id=0&qid=1751141875&sr=1-2-9e67e56a-6f64-441f-a281-df67fc737124&pd_rd_w=ANSuF&content-id=amzn1.sym.9f2b2b9e-47e9-4764-a4dc-2be2f6fca36d%3Aamzn1.sym.9f2b2b9e-47e9-4764-a4dc-2be2f6fca36d&pf_rd_p=9f2b2b9e-47e9-4764-a4dc-2be2f6fca36d&pf_rd_r=13W0N5WZ40KN26A0TTNR&pd_rd_wg=bRQIr&pd_rd_r=33487da5-bbf0-4322-95c1-7d0e203fea72

 

In my opinion, no. My '94 had almost 200K on it when I replaced them for CA smog inspection. My '03 Taco is running with the originals and passed CA inspection, I don't live there any more but every now and then run the OBD on it for codes. That is why I say suspicious. There's no harm in replacing them and you may be correct, they are the problem. I would download the FSM and see if it could be something else (I like to work from the items that attack my wallet least, first. )

 

TY for all of the additional info. Sorry for another dumb question @rocknbil. What is an FSM?

 

No worries, Factory Service Manual. Search TW, there will be links to downloadable version.

 

TY. Found and downloaded an FSM for P0136. Just read it and now I definitely feel like a novice. However, regardless of the complexity of the diagnostic process they describe it seems like the 2 common issues are either wiring/connections or the downstream O2 sensor. What I may do is do a close inspection for obvious wiring issues and if all looks good, then replace the O2 sensor. The diag process is definitely beyond me.

 

@Woodcutter, Thanks for the info and the link. The tool seems to be a 22mm socket but videos I've watched say the O2 sensor nut is 12 mm. I checked my TACO and it indeed seems to be 12mm. Am I missing something?

 

Huh, That’s a small nut, about 1/2 inch.

2002 V6 TACO.

Yours has two screws, one on either side.

So you’re good, see video.

The nut size is noted as a 12 mm as you stated.

3.4L V6 engine

https://www.youtube.com/watch?v=WXX8DXsNx3Y

4 cylinder engine

https://www.youtube.com/watch?v=SgbEmdjuzYk

 

If the nuts are a little rounded and won't come off, the trick I found was wire brush the rust off the exposed stud, apply penetrating oil, and use the smallest vise grips that are small enough to get a good turn on it in the small space with the nut so close to the sensor, and work it back and forth a couple times on the first thread when it starts moving.

 

Definitely plan on replacing the stud nuts when you replace the sensors. Even with little mechanical experience, replacing the sensors is something that you can do.

 

@Woodcutter, thanks for the videos. Watching them I figured out where the special 22 mm socket comes in. That would be the tool to remove just the O2 sensor and not the entire bracket and gasket which are attached with the 12 mm bolts.

 

Most welcome jcmatto2, good luck, may the force be with you.

 

I need to do mine and I was going to do the o2 and the air fuel at once. I saw the part number on another thread but i cant seem to find that thread. I think the part number for 1 of them is 234 -9003? I want the OEM ones. 3.4 V6 auto.


Thank you for any info.

 

The Upstream aka A/F sensor for an Automatic is

$146 234-9001 Upstream Air Fuel Ratio Oxygen Sensor with 10.6” 4-Wire Harness, for Auto Trans Equipped Vehicles

234-9001
We basically have the same truck. DC Auto
As for the Downstream aka O2 sensor.

$70 234-4189 Oxygen Sensor

234-4189
I haven’t replaced my Downstream one yet.




Note - the one you talked about

$170 234-9003 Air Fuel Ratio Sensor

234-9003 is for a manual transmission

 

Thank you very much. Your reply should be pinned. Thanks again.