Just a heads up, I bought two Denso A/F sensors off Amazon this past spring and when I went to install them one a month or so ago one was a dud right out of the box. Denso wouldn't warranty it because Amazon is not an approved distributor.
Did you try to return/replace it from Amazon. They tend to have a generous return policy.
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'96 T4R SR5 V6 Auto 2WD 329,000 miles
It was past their return window by the time it became cool enough for me to bother installing them.
Just curious...how exactly did you determine that the sensor was at fault? Did a second sensor fix the problem?
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'99 4Runner SR5 5spd 3.4L V6 4WD(U.S), original '99 Talls in front, OME 906s in back, Hella fogs, Trekmaster shocks in front, Billy in back, no running boards, FIAMM horns, Alpine sound, Michelin LTX M/S2's, owned since new.
'97 HiLux SW4 5spd 4WD(Japan model bought in Brazil assembled in Argentina, very close to a 3.0 4Runner/Surf)
'71 FordWillys Jeep CJ5 (with straight six Ford Maverick 3.0 liter engine--lives in the mountains north of Sao Paulo Brazil) My Backyard Frame Swap