p0135 2003 tacoma oxygen sensor

I followed several sites, testing as much as I could, I still cant figure it out. My connector has no letters or numbers that i can see for the four terminals. Still with key out none have voltage. with key to on, but engine off, I get 12.x, 2.x, 3.x, and 3.x for the four terminals. Now what?

tks,
p

 

infinite resistance across those two heater terminals of the front unit Bank 1 Sensor 1. So, I think its broken. Im going to get a replacement. First the junkyard, if swapping it makes the eng light go away, then I will buy a new one. I know the junkyard unit could be bad, but i dont want to spend the money on a new unit, until Im sure, that is the issue. maybe i get two at the JY.

AIR–FUEL RATIO (A/F) SENSOR Bank 1 Sensor 1

is above the same part as the rear unit?:

HEATED OXYGEN SENSOR Bank 1 Sensor 2

Also, what size the nuts? My 11 mm wont fit, but the 12 mm is very sloppy. Nuts are corroded a bit not that bad.

2003 toy tacoma 2.4L 56k miles.

tks much,
pa