tomf

I think of the A/F sensor as a more sophisticated O2 sensor. They are not interchangeable. Here's a link explaning A/F sensors http://www.motor.com/article.asp?article_ID=1643

Go to the Denso website to see which one you need. http://densoautoparts.com/find-my-pa...icle-selection

According to the Denso website, both your upstream sensors (Sensor 1) are A/F. Your downstream sensor (Sensor 2) is O2. Sensor 2 is on the exhaust pipe almost directly under the driver's seat.

If your error code is saying bank 1 sensor 1 (upstream rear) or bank 2 sensor 1 (upstream front) then you need the A/F. Note there are two different part numbers for the front and the rear upstream sensors.

artbuc

Only because the original wiring harnesses were different lengths. Quite sure these two p/n's have been merged, at least they have been on most 1MZ-FE's.

Mphidd

I just had all three oxygen sensors replaced on my 99 ES300 and that fixed the problem!! I love being able to exchange stories on this forum so we can help each other