CEL Codes P2238 and P0031. Opinions?

[04 Rocko Taco]

CEL P2238 and P0031 on a 2004 Tacoma Double Cab, 3.4 , auto. 200K on the clock (or damn near). No effect on mileage yet, staying right around 18-19 like always.

From what I am seeing half of the people out there say these codes refer to the O2 sensors, and half say it is the MAF sensor.

Need some opinions, and preferably facts from some people in the know.

Looks like an O2 sensor is running about 180 sor some off the shelf Vatozone crap.

Help me out here fella's.

Dont want to shotgun approach this.

[4x4mike]

I haven't had those code but I'd start with cleaning the MAF. It's darn near free and might save you some money. If you run an after market oiled filter I'd clean it or run a stock filter for awhile and see if it clears up.

If you need to get an O2 sensor don't get them from AZ. Got to Amazon and search for factory parts. You'll save a bunch and be money ahead from anything you get from a parts house.

[04 Rocko Taco]

Alldata on my shop computer lists both codes refering to the front a/f sensor.
0031 is for the a/f sensor heater circuit
2238 is an oem specific code that lists the heater circuit as well as some potential wiring problems.
The sensor has a heater circuit built into it to bring it up to operating temp faster than it would if it relied on just the heat from the exhaust. The computer isnt happy with this and sets the codes. The sensor still works properly and is why you dont see any performance or mileage issues. The only fix is a new sensor, its a pretty common problem especially if it is the origional one with close to 200k on the truck.

[4x4mike]

I have a 1999 4Runner and had to replace the A/F sensor last year. FWIW I did not have the codes you mentioned.

https://lh4.googleusercontent.com/-gkPFvnEeD6s/TbmXWVglMpI/AAAAAAAAlxg/yoGE975EXFU/s640/DSC08395.JPG

https://lh3.googleusercontent.com/-PF_PKQOQGmE/TbmXWsKTiKI/AAAAAAAAlxo/-PnjWy6t7iA/s640/DSC08396.JPG

https://lh5.googleusercontent.com/-0PlZdqgI76U/TbmXWLQbQaI/AAAAAAAAlxY/-mr8GgQyxIk/s640/DSC08394.JPG

Here is the new part with part number.
https://lh4.googleusercontent.com/-pyovcTJ9Kq0/TbmXTG7OIJI/AAAAAAAAlv8/ujeiuQJ72bk/s640/DSC08383.JPG

Old A/F sensor with obsolete Toyota part number.
https://lh4.googleusercontent.com/-dp3Y3P05RVg/TbmXVOT2hEI/AAAAAAAAlw4/67crwegTDKU/s800/DSC08390.JPG

[4x4mike]

I'm not at my computer that has the stored files on it but Avy might be of help. Here is my original post asking for advice for my trouble codes that resulted in an A/F sensor replacement.

http://www.ultimateyota.com/index.php?option=com_smf&Itemid=26&topic=9684.0

[YotaFun]

Check your wiring to that sensor, Bank 1 Sensor 1.
If all is good in the neighborhood your looking at replacing that Sensor Chris.

[04 Rocko Taco]

I have not even so much as glanced at the truck, but I assume this will be closest to exhaust manifold, correct? Not that it should be terribly close, but it should be the first one in line.

EDIT: I am attaching the schematic drawing, and the locations of parts from the FSM for the 5VZFE for future reference of those who may search and find this thread.

[4x4mike]

I've got a '99 4Runner, 3.4, with a 5 speed that is a CA emissions truck. On mine the front sensor is my A/F sensor (bank1 sensor1 on your second attachment). The plug for it is attached to one of the bolts (top) that holds the transmission together. It's near impossible, on mine, to access the plug end from under the truck. I had to go through the transmission tunnel under the shifter.

[04 Rocko Taco]

YES, I AM reviving a thread from 2012.

Finally getting on this repair 5 years later... yes, before you ask, I have been riding around with my CEL on for 5 years apparently.

Who do we know that does discounts on factory parts? Rafa and crew at NTP still hooking us up? What about Phil, or whatever his name was at Dallas Toyota? Anyone else I should be checking with?

[4x4mike]

I'd try the links Sean and I mentioned on the Facespace. I've ordered from both and have had good luck. The prices are less than dealer and they are genuine parts. I posted in my fuel injector post a few months back how there is some counterfeit Toyota stuff on ebay and Amazon.

[04 Rocko Taco]

Been perusing all the info I got over there, your links are where I'll probably hit.