o2 Sensor or Air/Fuel Sensor

Hi - I am about to replace the Catalytic converter on my 2nd Gen 2.7L Tacoma. Confirmed that old one is bad (it's been rattling around and have had loss of power). There are 2 sensors.

Sensor 1: Toward the Front (before the forward CAT). Is this an O2 sensor or an Air/Fuel mixture sensor? I've heard both, but wanted to be sure. Also - I know Denso is the Sensor maker - but would rather not pay Dealer prices. Anyone have an OEM - to Denso Direct part number?

Sensor 2: This one is behind the 2nd (rear) CAT. I am pretty sure this is an O2 sensor. Just wanted to confirm. Any OEM to Denso Direct part number?

What makes this confusing is the Part Diagrams with Toyota show 2 O2 sensors...in the engine compartment. Confusing.

 

The one towards the front of the exhaust, closest to the manifold is an A/F sensor. Denso is the best, but I have had great success with my customers and the Bosch brands. Rockauto.com will have all your parts numbers for you.

 

you will see various names and mistakes for the front and rear sensors
no matter what forum or doc you read on the web.

on older cars, both were O2 sensors, which is why the confusion

sometimes you have bank 1 and bank 2 (left and right side of engine)

in that case
you may have 2 a/f (bank 1 sensor 1 and bank 2 sensor 1)
and one o2, or two a/f and 2 O2 (bank 1 sensor 2 and bank 2 sensor 2),
depends on how the exhaust is piped/combined

in newer cars (since 1998)

the front one (before the cats) is an air fuel sensor, (wide band o2 sensor really)
it has far more accurate readings it sniffs, and it's job is to help ecu manage fuel
mixture accurately

the rear one (after the cats) is an ordinary old-school o2 sensor, which basically has a high
or low cutoff, and this is to sense how well the cats are working.

a/f is more expensive than o2, and you cannot mix them up, or you will
either a) not run b) run super rich or c) super lean

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Now the toyota ecu is extremely fussy that these be identical performing as stock, and there are tons of stories of NAPA or other sensors purchased that 'just don't work right' you cannot ever go wrong (except price) getting them at the dealer...so be careful where you do get them that they are guaranteed to work.

 

Yes, Rockauto will probably have Denso in stock!....

 

Thanks for the replies! Are the RockAuto ones exact OEM? Debating on replacing. I have 170K on the truck (no codes thrown) but I know the CAT is bad. Figured I'd replace them too since I can get to everything with the CAT out. But the price for OEM...geez. Another $200 on top of the $1300 for the CAT! ....wow.

 

Denso is the manufacturer for the Toyota O2 sensors and many other parts. In my opinion if you order the denso from rockauto it's the same part but without the Toyota logo/ marking. Basically, I think it's the same as OEM, but maybe there is a difference... Bamatoy may know the answer to that.

 

I just found the OEM (Toyota) Part numbers for Gen 2 - 2.7L at toyotapartszone.com:
For the benefit of others sense I couldn't find it on the forum.....

SENSOR, AIR FUEL RATIO (Upstream): 89467-04010 ($144.20)
SENSOR, OXYGEN (Dowstream): 89465-04320 ($107.70)

The reason these are so hard to figure out is they have them listed under Electrical > Switch & Relay instead of "emissions" or "exhaust". Go figure...

 

Not sure what the prices are at Camelback toyota but might be cheaper. Rock auto DENSO a/f sensor and 02 sensor are much cheaper than that. Guess it depends what you want to go with.

 

Hope folks are still on this thread and can help. My California 2000 3rz fe 2.7 manual 4wd Tacoma has (according to under the hood tag) 1 A/F sensor and 2 heated oxygen sensors and 2 cats. I see one o2 sensor downstream of 2nd cat and either an o2 s or a/f directly above the forward cat - where is the other o2 sensor or the A/f? Trying to order a part and it is a bear. Thanks beforehand for help

 

no you have 1 air fuel sensor in front of the cats and one o2 sensor after the cats, that is it

 

You are right! I goofed in my reading the tag. There is one af and one h20s. Thanks!

 

No, the Lower bank is 89465-04270 for Toyota Tacoma, 2005 2013 2.7