Here are a few pics of location and install of my O2 sensor on my 2004 V8 with 160K miles. This was the first one to go. Got the OEM Denso from Advance Auto for $98.00

I had to un-do the engine/flap/cover that protects the engine from mud/rain etc in order to access the sensor. Turned the tire so I could access it. Got a 22mm box socket wrench and with a few taps with a hammer-it turned pretty easy. I was worried that 160K miles of rust/debris would have sealed it in there, but with the engine hot....it was pretty easy to take out. Once out-I unhooked the opposite end that essentially is a cannon plug, it unsnapped from the socket and all was well. Install took approx 10 min once I had the correct tools. Went back to start it....the engine light and other VSC lights were on the dash and would not go out. Shut down the truck....un hooked the battery for 60 seconds, reconnected and restarted. All lights were out....SUCCESS!

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I am getting this code, I went to Advance Auto and they told me it was B1S1 for my 2004 Toyota 4Runner 4.7 Limited V8
The lady didn't know much about cars/trucks, she even had problems trying to plug in the computer to my truck port, I had to tell her that there is a cover on the port that has to be removed so she could plug in after watching here struggle for a few minutes. (I didn't want to be rude by telling her how to do it)
Anyways, she looked up on the computer for O2 sensors, I asked her for Denso (because of other driver reviews, its better than Bosch) she looked up Denso 234-4138 for like 70 bucks. I wasn't sure if it was the right one or not, so I am looking for some help.
I found this on Amazon which says "Fitment Notes: DENSO IS THE OE MANUFACTURER - UPSTREAM LEFT - UPSTREAM RIGHT - OE STYLE " for 59 bucks. not sure if this one needs splicing or not, I rather not splice.
is bank 1, sensor 1 on the upstream driver side?
is this the right image I am looking at?

Please comment back.

If you use the "Find Parts that fit your vehicle" option it will come up with 2 pages with about 15 different parts on each but if you pick one with the proper connector it should work without any splicing. Some come with a connector that you have to install but the Denso 234-4138 doesn't show any connectors so I'd be wary of that one. The Denso 234-4261 says it's ready to install but costs a bit more and several Bosch models such as the #13355 come with the connector ready to install for less money. I'd go with one that has the OE connector. I'm not sure about Denso being better than Bosch but I've always used Bosch and they have generally been OK.

I ordered this part (234-4138) off Amazon after checking both Amazon and Denso's website for correct part number. The part arrived and the wire was too short and the plug did not fit. I called the good old dealer and they said you need to order the part by VIN as there are several listed for the 2004 4Runner with the 4.7L engine. Shockingly, the dealer said the Toyota Part Number (8946560150) did not cross reference to a Denso part number even though Denso makes the part for Toyota. I called Napa for an NGK version and they said 5 to 6 days for $100. Ultimately, I bought it from the dealer since they could deliver the next day for $197!

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@ORTrail

That sounds pretty annoying... those dealer prices are really something else.

Thinking out loud here: If the sensor and plug was the same, it would have been little work to extend the wiring a little with some waterproof heat shrink butt connectors... cut and crimp.

That’s a good idea and I thought about cutting the wires and using the original plug with the new sensor which would give me the length I needed but wasn’t confident the sensor was the same. If it didn’t work I’d be back to buying from Toyota (or somewhere else) and I’d be out the Denso sensor $$. Sometimes the path of least resistance costs the most money, huh?

True on many counts.

Part (234-4138) is for bank 1 or 2 upstream only which are shorter length.

I just changed out the Bank 1 Sensor 1 on our 2004 V8. I mistakenly took out Sensor 2 and was bummed that I too had received or ordered the wrong part. The wire was too short and plug was incorrect. Wrong, I screwed up. I had previously read this thread in anticipation of changing out the O2 Sensor. After about 5 minutes of cussing under my breath, I discovered my error. Took out Sensor 1 and the new part screwed right in and plugged in without any issues.

I ordered a Denso part from Amazon. Delivered in two days and it was only $46, free delivery.

Phil

I have a 2003 V8. Check engine light, vsc trac and vsc off lights came on. Code shows P0031 and C1201. Replaced drivers side upstream (pre cat) with Denso 234-4138 from Advanced Auto for I think $85. It was a perfect match for what I took off. Unhooked negative cable for 60seconds, started her and no more lights. Drove around for 15min and no problems. Fingers crossed!

Thanks for the pictures on the original post.

Confirmed on this. Had the P0031 code for a while, indicating the Bank 1 Sensor 1 (upstream to Cat) was faulty. Went straight to Amazon and bought the Denso 234-4138 sensor for $40 with Prime delivery.
Removed the engine bay flaps.
Sprayed the old sensor with PB Blaster. Unscrewed the old sensor, disconnected the connector on the bottom (be careful not to break the plastic on the receiving piece).
Installed the new sensor and boom....CEL is gone!

TL;DR - If you are getting a P0031 code - IT IS BANK 1 SENSOR 1, and DENSO 234-4138 IS 100% THE SENSOR YOU NEED.

Not sure why so many folks were confused by this or said it didnt work...This is the drivers side upstream sensor, technically considered AFR - Air/Fuel Ratio sensor.

CLICK HERE FOR LINK TO PART ON AMAZON

Your link isn't working. Mind fixing it??

Oops! It's now updated.

I'm trying to change the same O2 sensor on my 05 v8 4runner and the O2 sensor looks like its totally in a different location. Mine sits on top of the cat and sits more behind the engine which is a pain to get to. Any clues on how to get this guy out?

Any help? I need it. It’s way up there