How to replace O2 Sensors

It worked great, changed the up stream and down stream oxygen sensor in about 20 minutes thanks for the advise.

Curt

 

Here it is 2016, and my engine light lit on my 2002 Taco. 6cyl double cab off road. I got an OBDII reader from Amazon. Inexpensive ELM 273. Downloaded free app, sync to phone. Voila bank 1 sensor 1 air/fuel sensor. Purchased denso sensor less than 100$. Of course am having devil of time with the connector. The sensor was replaced before so the bolts aren't too bad. Your pics are absolutely great, thank you. Does anyone have a pic of the OTHER side of the connection- that goes to engine block? I tried to view it with a small mirror but couldn't get a good view and my phone doesn't fit it there. My other option is to go in from console, which since its raining here might be a better idea, but seems that it would take more time. I love this truck and I used to go to a shop, but realized the right parts aren't always used, so I try to do what I can, to save $ and do it right. Appreciate any help I can get.

 

Go through the shift console it works great

 

This is off a 1996 taco with manual tranny.

http://www.lieblweb.com/o2replacement.html

 

Great write up, as I used this as resource when changing the upstream sensor.

 

Doing this now on my 2002 Tacoma 3.4L V6 manual trans. Had 1 question and thought I'd add a couple pictures to the thread. As said, it's a PITA to get to the upstream sensor connection. I went through the gear shift access hole. It took me some time to realize the connection was facing the opposite direction even though I read it previously in one of these discussions.

The first picture is trying to show the plastic connector that connected the wiring harness to the transmission. I took a flat head screw driver and a hammer and busted it so that I could turn the harness around and access the O2 sensor connector. (the pic is after all this, that blue/black/white wiring you can see is the O2 sensor wiring after I've turned the harness around.)

2nd pic is just another of the O2 sensor connector for visual. I wish I had gotten a pic before I turned it around but did not. Tip for me: having the O2 sensor un bolted gave me the proper slack I needed to turn the connection around.

The 3rd pic is my question. I don't know if in my struggles to get to the O2 connection I knocked this connection loose, but I can't seem to locate where it goes. Can anyone give insight by looking at the connector to where this came from? This really is a poor design flaw having all this stuff tucked away above the transmission.

Thanks,
Nick

 

Just replaced my B1S1 Air/Fuel Ratio sensor a couple days ago and have a few comments about my experience.

First, spray a penetrating oil on both nuts and bolt threads a couple times, letting them "soak" for a few hours each time. Don't rush. This will prevent a broken stud, which complicates the replacement a thousand-fold and significantly impacts overall cost and down time.

Second, use a socket if possible. I was only able to loosen and re-tighten the nut one click at a time, but as I said earlier - don't rush the job.

Third, the wiring harness connector has a nipple, fitted to a mounting bracket, which you should disconnect that allows much more freedom to remove and replace the O2 sensor connector. Remember to click it back into place when you are done with it.

Fourth, the gasket will have heat material on both sides, one side is almost fully covered (this side goes towards the exhaust pipe) and the other side is only about half covered (this goes on the sensor side).

Fifth, apply anti-seize to the bolt after the sensor is in place to ensure NOTHING gets on the element, including you grimy fingerprints (use gloves). You can also apply some to the nut.

Lastly, do not over-tighten the nuts, or you may snap a bolt off (see above). Check for leaks after install by starting engine.

 

I also thought by looking at how dirty the mystery connector looks that it may have not been plugged into anything...

 

I'm getting ready to dive into this job as soon as my Denso sensors come in. Unfortunately, I didn't see this thread, and I rushed and ordered the wrong upstream. (

$137 234-9001 Upstream Air Fuel Ratio Oxygen Sensor with 10.6” 4-Wire Harness, for Auto Trans Equipped Vehicles

234-9001, instead of the

$170 234-9003 Air Fuel Ratio Sensor

234-9003 for my manual transmission.)

But I appreciate all the photo's you all have included, and the detailed write up. I noticed that I could not find any youtube videos on this, so if I get time, I may try to record the process.

Thanks again!

 

Thanks for all the info guys!

Super simple to replace... but if your nuts are a rusted mess its more involved (mine were completely toast). I hit them with PB blaster for a few days, then filed them down so I could get a smaller sized wrench around them. I didnt have access to a torch or grinder. Cleared up my P1135 code.

$137 Denso 234-9001 Upstream Air Fuel Ratio Oxygen Sensor with 10.6” 4-Wire Harness, for Auto Trans Equipped Vehicles

Denso 234-9001 Air Fuel Ratio Sensor: $96.00
OEM Replacement Nuts: $5.58
PB Blaster: $3.76
Anti Seize: $1.49

 

Used this post today. Only thing that took time was the connection, didn't want to separate

 

Since you have a 2.7AT like me

For bank 1 code error, did you replace both upstream and downstream?

For the upstream plug did you have to relive your consoles?

 

got checked engine light last night. Truck only have 76k miles 2.7 AT. Pulled code P0125, P1130, and P1135. Im leaning towards the O2 sensor, but I will Ohm it out first.

Ebay have

$137 Denso 234-9001 Upstream Air Fuel Ratio Oxygen Sensor with 10.6” 4-Wire Harness, for Auto Trans Equipped Vehicles

Denso 234-9001 for $42-66 shipped.

 

Hi I am doing my bank one sensor one O2 sensor now on my 02 Taco 2.4 AT and I hope some one can help me with a question. I soaked the bolts and they both came off nicely. I bought a

$61 Denso 234-4189 Oxygen Sensor

Denso 234-4189 off EBAY. The sensor on my truck goes about a foot and then a clip on the end connects into another clip. these clips are held in place by another clips attached to something up there. When I pulled the new one out of the box it is about 24" inches long with no clips except at the very end with a rubber boot. Do I have the worng sensor? I double checked compatibility and it said it is compatible with my vehicle.

 

You ordered the downstream sensor

 

Ok thats what I was thinking too. After I wrote the question I went back out and looked at the downstream sensor and thought "I bet I ordered that one by mistake. No biggie, I read that if one goes bad there's a good chance the other one is not far behind and some said you might as well do both. I will hold onto to it. Do you happen to know the right Denso part number for the upstream sensor?

 

$153 234-9002 Air Fuel Ratio Sensor

234-9002 for auto

$137 234-9001 Upstream Air Fuel Ratio Oxygen Sensor with 10.6” 4-Wire Harness, for Auto Trans Equipped Vehicles

234-9001 for manual

 

Thank you very much!!

 

Do you know who has them for the best price?

 

Up on post number 26 of this thread, a question was asked as to where that mystery plug went to. I unfortunately broke the o2 sensor plug on the trucks wire loom so I had to go find a Chiltons book and find out which color wire did exactly what and direct wired it to the new o2 sensor. If anybody else breaks their o2 sensor plug the color code is as follows when hooked up to a

$53 denso 234-4161 oxygen sensor with 15.35” 4-wire harness

denso 234-4161 o2 sensor.
Brown is definitely ground
White /red is power
Pink to green stripe heater to ecu
White is oxygen wire to ecu

O2 sensor colors as follows:
2 blacks go to heaters to pink and white
White goes to brown
Blue goes white/red
I wired straight through to "butt" connectors and ditched the stupid proprietary wire connector. Where does that other mystery plug plug into as I took my truck for a test drive before I put rubber boot and center console back together to find out that my speedometer all of a sudden doesn't work, so I'm assuming that mystery plug is for the speedometer. Now I just got to figure out where to plug it into before a button up my center console. This o2 sensor replacement has been an absolute nightmare. Thank goodness I found that wire diagram for the upstream o2 sensor, otherwise, I'd be screwed. Hopefully me posting that will help someone if they accidentally pull their plug off and are in the same boat as I looked all over the internet and could not find the answer. I was starting to get worried.