Like many on here, I have the persistent p0171 error code I am chasing on my 1999 ES300. I cleaned the MAF and that bought me about 2 weeks of relief then the code came back. I replaced the MAF and got about a week of relief. I am now going to try replacing the bank 1 o2 sensor. I came up with Denso part number 234-9007 and ordered it from eBay. Well, the part showed up today and it is 234-9021. I am waiting to hear back what the vendor says, but is this a replacement part number?

 

OEM Part #: 89467-41040
MSRT: $206.36
Your Price: $ 139.99 w free shipping
2000-2003 TOYOTA SIENNA 3.0L
1999-2001 LEXUS ES300 3.0L
2000-2004 TOYOTA AVOLON 3.0L

 

According to RockAuto 234-9007 is the way to go (they sell it for $116.79 + shipping). Seller either sent you the wrong part, or it's a generic knockoff. Lots of "Chenso's" on eBay nowadays.

 

Denso makes these OEM parts for Lexus.

I used Denso 234-9021 air/fuel sensor on my ES (2000) :
Also used Denso 234-4137 oxygen sensor :

 

Looks like they just sent the wrong part. i am exchanging it. Thanks all!