Can anyone tell me where it is on a 1991 Lexus ES250? Is there a link to a DIY on replacing it?

 

Without knowing anything about your particular model, its sticking out of the exhaust manifold under the hood, lol. In general, theyre pretty easy to replace, disconnect the wire and use a 7/8" o2 socket [from napa, autozone, kragen, walmart] to remove it.

http://www.scoobymods.com/oxygen-sen...02-t5464.html?

That thread has some general info about removing 02 sensors on different car models, but theyre pretty straight forward. The link below came up in a part search for your model.

http://www.amazon.com/Denso-234-4051.../dp/B000C5YCO8

 

Thanks. I've been having trouble figuring out if my car has one or two O2 sensors... most people say it has two, but so far from looking for parts I only find one?

 

I was able to find the service manual for your car. The es250 has a 2vz-fe engine.


http://www.ebooksquad.com/2009/01/31...ce-manual.html

Go to that site and click download. It is a zip file. Inside there is 3 PDF files, one is engine.

Open up the engine file which is a guide on how to fix, repair, locate different stuff in your car engine.

The above repair manual refers to the "main" and "sub" sensors. The "main" is in the engine, and "sub" underneath the car after the catalytic converter.

If you open up the engine PDF file, on page 176 and 114, gives you an idea of where the "main" sensor is. Page 173 where show where the "sub" censor is. You want to replace the MAIN one.