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Discussion Starter #1
So why do they always go bad and these things are in terrible places to replace and cost a fortune due to having to replace them is pairs? Is it worthless ethanol laced gasoline or just PP quality parts? Are they made by the same company that makes the Lower Ball Joints?:confused: My 06 has not had any issues yet but ethanol gasoline is all that is sold in NM except for 4 places which are way too far to travel for a fill-up!
 

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They usually last quite a while actually. My first one went at about 90K. I changed
it's "partner". The post converter one didn't go until a while after that, and
I changed its "partner" too. I did three of the four, as the fourth was seized into
the manifold, however I bought that one online and saved money. The dealer
had no problem putting it in as it was OEM.

The four I bought cost me what two would've cost at the dealer, just for the
sensors. Never mind the labor if I had them do it. The ones in the manifold
can definitely be a PITA, but the other ones aren't bad.

John
 

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So why do they always go bad and these things are in terrible places to replace and cost a fortune due to having to replace them is pairs? Is it worthless ethanol laced gasoline or just PP quality parts? Are they made by the same company that makes the Lower Ball Joints?:confused: My 06 has not had any issues yet but ethanol gasoline is all that is sold in NM except for 4 places which are way too far to travel for a fill-up!
If you take the skid plate off of your truck and use the right combination of extentions and one of those swivel tips or swivel joints in your set of extentions you can get to the sensors in the manifold without too much trouble. I replaced both of the sensors in the manifold. I had my brother line the socket wrench with the combination of extentions on it up with the sensor and i twisted the wrench. it beats the hell out of paying the dealer to do it and only takes 30 minutes from start to finish on a bad day.

oh, you also need to buy an oxygen sensor socket at autozone. iirc they are only about 10 bux and worth every penny.
 

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Just seems like their would be a reason that these things go bad and i understand how to change them and i do not understand why they go bad? My sensors are working fine but ya just read on here that so many people have to remove and replace them and what makes them go bad? :confused:
 

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2015 Toyota Tundra DC SR5 5.7L
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Just seems like their would be a reason that these things go bad and i understand how to change them and i do not understand why they go bad? My sensors are working fine but ya just read on here that so many people have to remove and replace them and what makes them go bad? :confused:
I have seldom seen where members are reporting that the sensors are failing at significantly low mileage intervals. Anecdotal evidence puts failures right around the expected life of a heated air-fuel/oxygen sensor, namely 90,000-100,000 miles.

FWIW, it is my opinion that the major reason that the fuel/air (upstream) sensors fail has to do with 1) burning chemicals other than gasoline, i.e. all the "cleaners" that seem so prevalent in forum discussions. I think very few are completely used in the combustion process and these chemicals run the risk of sooting/caking on the intake ports and/or electrode element inside the sensor unit; and 2) environmental issues, i.e. effects from caustic road salts, mud, etc degrading the metallic components inside the sensor unit's electrical connector.

The two biggest suggestions to maximize life and/or workability of the sensors -- especially the upstream units -- is to 1) make sure to install these components with anti-seize on the threads, and 2) if you foresee ever driving the vehicle in harsh environments (road salt, mud, dirt, etc) pack the connector assembly well with dielectric grease beforehand.
 

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Discussion Starter #6
Did not know these things had an expected failure date/mileage attached to them and i was thinking also that some fuel additives could be causing issues maybe. i do run Techron thru my fuel system on occasion and i also use Lucas fuel treatment when i do not use the other but i do not use it every fill-up! So you guys with sensor issues when did yours start going bad? I would think that these things would last a lot longer than 90 or 100K but obviously they probably have not? I guess i need to call Denso and talk to an engineer and ask them whats up with these things and why their job security is not in jeopardy! So 90 or 100K is acceptable time frame for sensor failure?:beatsme:
Seems the link below mentions reliability ratings on the 2000-2003 Engines as having issues with Oxygen sensors and i guess most of those would be high mielage trucks but i do not think all of them have been high mielage truck that have had this issue?
http://autos.msn.com/research/vip/Reliability.aspx?year=2000&make=Toyota&model=Tundra#Engi
I guess the link below explains why some go bad?
http://www.densoaftermarket.com/oxygen-sensor.php
 

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Discussion Starter #7
Anecdotal evidence would suggest that i never mentioned in any of my post at what mileage these things were going bad but it seems you have given them a failure rate! There is evidence of reliability on certain model Tundras in which they have known failures and as i mentioned they were the 2000-2003 and i have read a post on TS of a 2004 having issues. Search for oxygen sensors pulls up like 13 pages of hits and no i have not looked at all of them but being exact and scientific is probably not my forte:p
I suppose as mentioned that addatives, oils, and the like casue these items to fail as mentioned on the Denso site i linked in their first paragraph?
 

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Hogwild, I hope you are buying denso sensors in the aftermarket. They are the oem supplier and run about 65.00 from
parts houses. 130.00 a pair is not free but certainly not a terrible blow. Take your tire and mud shield off and change the front two through the wheel well. It's a very easy job.
 

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I am confused why you guys think my oxygen sensors are bad? I just want to know why everyone else seems to be changing theirs? MY SENSORS ARE NOT BAD!!!!
 

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I replaced the passenger's side sensor on my truck at 36,000 miles. No where close to the 90-100,000 figure given here. I also have a Camry and have replaced the same sensor twice under 100,000 miles. I have to agree that they do eat up sensors for one reason or another.
 

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My truck had a 02 sensor failure at 121k. That was the first check engine light I had seen. 7 years of driving it like I stole it. My friends with fords and chevy's would be jumping up and down to get 60k and no check engine light. Hell my ex had a 03 dakota that she had to have towed to the dealership twice before she got to 20k. So if you have to replace 02 sensors every 100k just be glad it is not a dodge on a hook.
 

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The 90,000-100,000 MTBF rate is for the heated (3- or 4-wire) O2 sensors used in our vehicles. Other makes use the unheated (2-wire) sensor units and these go about every 25,000-30,000 miles. By comparison, we can count ourselves lucky.
 

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Part numbers for the Denso, please?

Thanks,
Roberto
 

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Location

I just read through the Field Service Manual, and I can't find the front O2 sensors. It shows the back ones riding on the converter, but no front ones. It shows A/F sensors in front. Could this be it with a different name?

Thanks,
Roberto
 

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Mike,

I didn't explain myself, sorry.
I meant that I can't find their location on the engine. I see the rear ones, but no front, unless they are the A/F sensors.

Regards,
Roberto
 

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Mike,

I didn't explain myself, sorry.
I meant that I can't find their location on the engine. I see the rear ones, but no front, unless they are the A/F sensors.

Regards,
Roberto
The front (upstream) sensors, located at the rear of the exhaust manifolds just forward of the pipe flange, are correctly referred to as "fuel/air sensors" as they determine the optimum fuel/air ratio for engine management. The rear (downstream, after-cat) units are accurately known as "oxygen sensors", and they report back emission info to the CPU.

Colloquially, they are all known as "oxygen sensors".
 
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