Both front 02 senors failed at the same time

[OilAnal]

Hi, I have a Camry V6 3.0L. Every year I drive down to Texas from Colorado during the holidays. This time, my check engine light came on and it took the replacement of both front (pre-cat) O2 senors to get the light to stay off.

It seems kind of strange that both would fail at the same time around 70k miles. Just bad luck or was it the increased O2 at the lower elavation that put the senors over the top. Also, the gas MPG seems slightly lower now by a few MPG with the new senors, which implied the engine was running real lean with the old O2 senors, but with no Ck engine light in Colorado with the old O2 senors.

Thanks for any input.

[ January 03, 2004, 06:31 PM: Message edited by: OilAnal ]

 

[TheLoneRanger]

OA, did you have the codes read? A trouble code that indicates a bad O2 sensor would also state the bank that the sensor is on; bank 1 or 2. Maybe the first replacement was of a working sensor, and the second replacement was the one that was actually bad, and turned off the light.....

Usually a new O2 sensor will give better mpg. When one goes bad the engine defaults to a pre-programed air/fuel table which is usually on the rich side.

 

[Robbie Alexander]

quote:

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Originally posted by OilAnal:
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It seems kind of strange that both would fail at the same time around 70k miles. ------

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Sounds wierd but possible.
My originals went at EXACTLY 60K to the mile.
I think they must be programmed or designed... because all replacement go out almost or directly to the mile of either 60K or 70K or 80K depending on the O2... with my truck.

Now, as far as poor mpg... possible cat>??? or maybe you bought a generic O2 or a Universal o2 instead of Toyota? When I replaced my Bosh "oem" with a Toyota OEM I noticed 1. The toyota one is heavier, and 2. I felt a better response - BTW the replacement was per a maintenance not because of failure.

 

[Steve S]

Sometimes I just bite the bullet and go to the Toyota dealer and tell them to diagnose, and tell me what needs changing and why then decide on what you want to do. It will cost some labor time but if the techs are good they know what it takes, cause they work on toyotas 8 hours per day.

 

[Robbie Alexander]

quote:

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Originally posted by Steve S:
Sometimes I just bite the bullet and go to the Toyota dealer and tell them to diagnose, and tell me what needs changing and why then decide on what you want to do. It will cost some labor time but if the techs are good they know what it takes, cause they work on toyotas 8 hours per day.

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Yeah. well maybe. It depends on the Tech guy.

I was at the Dealer Friday trying to search for theis CAT code that keeps tripping the check engine light... They suggested that it is the CHARCOaL Canister... I might buy it, but I talked later to an EXXON mechanic about three miles later, and he said he has had several Tacomas come in with the same problem, 1995, 1996, 1997
ALL at 60K. All had a couple CATS installed and all had new front O2's and all did not have the rear O2 replaced... Although the code never tripped for the rear per se, the Scanner had a text file in it for the Tacomas noting that in many cases first replace the rear O2 before deciding to condemn the CAT or look elsewhere.
He told me that in all those cases it FIXED the problem.
Well I ordered one based on his info. 5 miles later the light turns itself off, like it did before... I hope this fixes it, I'll try the charcoal next and if not I guess I'll have to go to the dealer because everything else has been replaced. All along the dealer and other mechanics have told me they can't find anything wrong with my truck and point to the cat and naturally the cat guy points to the mechanics, I am CERTAIN it is everyone not knowing a DANG thing about any of this matter... everyone is ignorant and won't admit it, That's my opinion...
IT is often left up to an experienced tech man.

 

[OilAnal]

Thanks, Some info. I had the Toyota dealer read and used Toyota repacement senors. Checked owners manual, no scheduled replacement for O2 senors. Really good car, other than scheduled plugs, this car has had only good maintentance and no other problems.

Should I go ahead and just replace the post-cat O2 senor and just treat O2 senors as normal 60K+ maintentance?

[ January 04, 2004, 01:38 AM: Message edited by: OilAnal ]

 

[JohnBrowning]

I've got one for ya's. My Dad has the mid model year 1995 Tacoma and he has only had to chage the O2 sensor once in 130,000-150,000 miles. It was changed under warranty and they only had to change one of them.

I agree that the aftermarket Bosch O2 sensors do not seem to last as long as OEM. Remember guys emmision equipment now has something like 80,000 mile warranty from OEM. DO not pay to do it your self if you can get it for free!

 

[wulimaster]

For those who has O2 sensors go out in 60k miles, I was wondering.

Were you running synthetic oil in the crankcase or dino?

I have 110k+ miles on my Toyota pickup and my last emission test last July showed my truck to be burning clean and lean, and I have yet to touch an 02 sensor or cat.

25k oil changes on Amsoil 10w30. Last change at 10k because of antifreeze contamination during timing chain and guides replacement at 110k miles.

 

[OilAnal]

I did have 3 oz of Auto-RX maintenance and about 6oz of #132 in 5qts Mobil1 5w30. Also, #131 12 oz in 18gal tank.

[ January 05, 2004, 01:51 AM: Message edited by: OilAnal ]

 

[wulimaster]

quote:

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Originally posted by OilAnal:
I did have 3 oz of Auto-RX maintenance and about 6oz of #132 in 5qts Mobil1 5w30. Also, #131 12 oz in 18gal tank.

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I meant for the whole time you had the car as opposed to just the last oil change. Sorry for not being clear.

 

[Robbie Alexander]

quote:

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Originally posted by OilAnal:
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Should I go ahead and just replace the post-cat O2 senor and just treat O2 senors as normal 60K+ maintentance?

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When I first got my truck and it went out I discussed it with the Dealer Service Manager and after with several Mechanics. A lot will say just wait til it goes out. Me I like to be more pro-active.
From what I gather the back one will either give immediate probles soon after replacement of the fronts or not. In most cases, they tell me the REAR will last 2-3 times as long... most say replace the rear 1. When the CAT is replaced or 2. Every 2-3 Front o2's.
I have followed neither, and have nothing but problems. I am now in the process of following this suggestion... I hope it will help. Sometimes, the tech guys do know something

 

[OilAnal]

Wulimaster,

Sure, the car except for first 2k break-in has been ran with Mobil1 5w30 or 10W-30 usually at 3k miles(yes, still not convinced that 3k does not have some advantage however small) and Mobil1 ATF or Redline D4.