V8 Oxygen sensor replacement P0031, did I get the right part? - Toyota 4Runner Forum

apv97 · 08-21-2022, 12:57 PM

My CEL+VSC lights came on this week on my 2004 V8 T4R. Autozone scan tool showed code P0031 "heated oxygen sensor heater control circuit low bank 1 sensor 1"

My old gas cap doesn't seal well so I already ordered a replacement, but I need to tow 6k lbs over the mountains in 5 days so want to go ahead and take care of the oxygen sensor just in case it's that and not the gas cap.

I've been reading existing threads but am seeing different part numbers and conflicting info.

1) Is this the right part? Upstream Denso sensor part 2344138 or this one - AFR Sensor 2349047

2) Anyone have a diagram or video showing which one is which? Want to make sure I'm replacing the right one. Apparently there are at least 4? Maybe 5?

Thanks

Buckaroo · 08-23-2022, 07:35 AM

Quote:

Originally Posted by apv97

My CEL+VSC lights came on this week on my 2004 V8 T4R. Autozone scan tool showed code P0031 "heated oxygen sensor heater control circuit low bank 1 sensor 1"

My old gas cap doesn't seal well so I already ordered a replacement, but I need to tow 6k lbs over the mountains in 5 days so want to go ahead and take care of the oxygen sensor just in case it's that and not the gas cap.

I've been reading existing threads but am seeing different part numbers and conflicting info.

1) Is this the right part? Upstream Denso sensor part 2344138 or this one - AFR Sensor 2349047

2) Anyone have a diagram or video showing which one is which? Want to make sure I'm replacing the right one. Apparently there are at least 4? Maybe 5?

Thanks

I have not done this job yet but there are a couple of sources I look at for this type of info. For a 2004 T4R V8, The Densoautoparts.com web site shows the upstream OE style O2 sensor as part 234-4138. Not sure if you need one or two, will check. Downstream there are definitely two (likely due to different pigtail length) - the left one is 234-4261 and the right one is 234-4260. I also always check Rockauto to confirm (and it does). It lists these Denso part numbers and includes a generic schematic. I have included link to catalog and part specific web pages. FYI, I don't see the 234-9047 that you identified listed on either site for an '04 T4R V8.

2004 TOYOTA 4RUNNER 4.7L V8 Oxygen (O2) Sensor | RockAuto

More Information for DENSO 2344138

More Information for DENSO 2344260

https://www.rockauto.com/en/moreinfo...2Brfuk8CimZN6U

Buckaroo · 08-23-2022, 07:57 AM

Attached schematic from FSM shows two upstream O2 sensors located on the manifold (referred to as A/F (Air/Fuel) sensors) and two downstream located on the downstream side of the CAT. So the two upstream are the same part number, the two downstream are two different part numbers. That P0031 code is for the upstream O2 sensor (also called A/F sensor) on the drivers side. Long story short, Denso 234-4138 is the one you want. You might want to consider replacing both those upstream sensors. Good luck!

apv97 · 08-23-2022, 09:13 AM

Thanks Buckaroo,
I ordered 234-4138 so that's good. That schematic is helpful but also muddies the waters a bit...the Autozone code reader refered to my P0031 code as "Heated oxygen sensor heater control circuit low bank 1 sensor 1" which is kind of a mix of the language of the two driver side sensors. Nothing about A/F sensor..?

And the other threads say you get to it by accessing through the wheel well. However in this diagram the A/F sensor seems like it may be accessed via the hood.

Buckaroo · 08-23-2022, 01:30 PM

Quote:

Originally Posted by apv97

Thanks Buckaroo,
I ordered 234-4138 so that's good. That schematic is helpful but also muddies the waters a bit...the Autozone code reader refered to my P0031 code as "Heated oxygen sensor heater control circuit low bank 1 sensor 1" which is kind of a mix of the language of the two driver side sensors. Nothing about A/F sensor..?

And the other threads say you get to it by accessing through the wheel well. However in this diagram the A/F sensor seems like it may be accessed via the hood.

Not mixed - Bank 1 Sensor 1 is the A/F sensor on the driver side. A/F sensors are just a more sophisticated oxygen sensor. The more specific name is A/F sensor but lots of people just generically call them oxygen sensors. See additional detail attached on P0031. You can't tell from that diagram where you access it - it may very well be through the wheel well. That is where I would start. It would be on the manifold in front of the front CAT.