Which sensor to replace?

Now I need some help. Heres the code, P0031 HO2S Heater Control Circuit Low (Bank 1 Sensor 1). Now what I need to know is this. Is there more than one H02Sensor infront of the cats, because of the V6 having a left and rightexhaust pre catalytic? I ask because I have not been under the vehicle to look at the scenario yet. I have looked through some of the threads and the replacement seems straight forward. Somewhere someone mentioned a spray to place on the nuts as I think this is not a threaded sensor but a double studed one. Does Bank 1 refere to a side of the vehicles exhaust?

A little history. I went to schucks/ now OReilly, and checked the code for free. I didnt want to give toyota a ton of bucks for the pleasure of testing. I just need to know which sensor to buy and I'll do the work. Pisses me off cuz I just got done paying them for the 92,000 timing belt swap, 850.00 plus a bunch of other stuff.

 

Thanks thats great to know. I'll go get a Bosch and get r done
Unless anyone suggest going to the dealer on this. Rockauto?

 

Don't get a Bosch, get what originally came on your truck, Denso. It costs a bit more for a reason.

 

Rockauto has the Denso part # 2349001 pre cat part for auto trans models for 143.00 . Gasket 8 bucks. What was the name of that spray to put on the nutz. You guys rock, so glad I found this sight.