Air fuel ratio sensor vs. oxygen sensor


I have a 2002 toyota doublecab prerunner, 4cyl, autotrans. CEL on, dealer and autozone both pull same code, I think 0135. Basically, bank 1 sensor 1. I can see one sensor before the CAT and one after. Toyota says I have a third one. they say it is before the cat and on the exhaust manifold. I don’t see anything there. I haved moved on believing the dealer to be either incompetent or dishonest. I have decided that I should replace the sensor before the CAT. I got a Bosch from autozone 13613. It is called an oxygen sensor. Toyota claims that my truck, which is not California emissions, takes an air fuel ratio sensor (which I know is a glorified O2 sensor. In several online catalogs I can find both types of sensors to fit my truck. They make no mention of California. How do I know which one is correct. I have scoured the net and discussion forums to no avail. Any help would be greatly appreciated.


You were correct to move away from that dealer. The O2 sensor is what monitors the air/fuel ratio. I don’t have my code book handy, but just make sure the code points to the correct sensor, either sensor 1 in front, or sensor 2 in the back. California emissions were stronger than the rest of the nation, but have come ‘in-line’ with the rest of the nation once ODB-II was adopted in 1996. BTW, get a Toyota sensor to avoid any problems. I tried a Bosch sensor in my Supra, and it was bad from the start. Cost me a lot in un-necessary repairs.


I did a quick internet search regarding this problem and found the following on another forum. Take note:

“Be very careful when buying something from anyone other than Toyota to replace an air/fuel ratio sensor. Autozone (and others) will be glad to sell you an “oxygen sensor” for the application, at a cost of maybe $80, but it WILL NOT WORK. (Ask me how I know.) Toyota went to a 50-state emission build during the 2001 model year, and most or all 2001-up Siennas require the A/F ratio sensor. The car’s engine control module knows the difference and the code(s) will persist. The correct sensors list for at least $200 each; I found one for about $153.”


All “oxygen sensors” are NOT the same. They DO measure oxygen content; but, in different ways. The engine computer can not recognize any type of oxygen sensor for which it has not been designed.

Here is an informative article about different types of oxygen sensors at wikipedia:

Here is a tutorial about oxygen / air fuel ratio sensors, by Toyota:

I think this “wide band” oxygen sensor, at Auto Zone, should be ok:,APP228848/vehicleId,2746401/initialAction,partProductDetail/store,1140/partType,00117/shopping/partProductDetail.htm