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‘04 Tundra 4.7 186k in rust belt western PA with original downstream O2 sensors. I think my bank 1 side failed because I’m getting a P0420 bank1 catalyst below threshold but the Cat seems ok. (No loss of power or mpg, downstream side is 20 to 25 degrees hotter on infrared temp scan). My exhaust looks pretty solid even around that area all things considered. My question is how hard are they to remove? Can I expect to ruin something? I soaked it this evening while hot with PB Blaster. What wrench do you use? My slotted 7/8” socket that I think I bought for another O2 sensor somewhere along the line is too big. 19mm open end that I used just to check for size didn’t seem to fit. Relax, I didn’t try to loosen it with an open end wrench. ; ) The connector did come apart easily though.
 

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Discussion Starter #2
Anyone?
 

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You've been a member on this site for over 16 years and you dont know how to use the search function? Plus you already have a thread going about whats wrong with your 02 sensors and you have people helping you out, why didnt you just ask there instead of starting a new thread?

This took all of 1 minute to find.

 

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My apologies and thank you. I posted it right before bed because I had to get up early and had a limited window of time. And I was mistaken in thinking the sensor itself unscrewed from the flange. It was dark when I looked at it and I didn’t realize the threaded studs were holding it in.
 

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No worries Eric. By no means am I trying to be an A hole when I wrote that so please dont take it the wrong way, just thought it strange a veteran of the site wasnt able to find an existing thread. Hopefully that one helps you find your answer.
 

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No worries. I deserved it and the world has become too sensitive anyway. In the meantime now in the light of day I see the problem. One nut was rusted off and gone, while the other rusted partially through and was loose. I’m sure a leak was causing the fault. The sensor came out super easily and the studs seem solid and intact. Probably not even a bad sensor but now the gasket is shot so I need a replacement plus 2 stainless nuts. Should be an easy fix. Not worth waiting for a gasket. Gonna just put a new sensor in.
 

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And seeing your cheapskate username, I can easily identify. Trust me I’m tempted to just try and fix the gasket but I doubt it will work.
 

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Discussion Starter #8 (Edited)
In fact now I’m inspired. I scanned the engine yesterday and noticed both downstream voltages were fluctuating more than they should. I just checked the other side and found the same problem just not as advanced. Found 2 gaskets locally. Gonna swap them out with new nuts and see what happens.
 
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Well hopefully you can get it fixed, and for the least amount of money possible. LOL.
 
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‘04 Tundra 4.7 186k in rust belt western PA with original downstream O2 sensors. I think my bank 1 side failed because I’m getting a P0420 bank1 catalyst below threshold but the Cat seems ok. (No loss of power or mpg, downstream side is 20 to 25 degrees hotter on infrared temp scan). My exhaust looks pretty solid even around that area all things considered. My question is how hard are they to remove? Can I expect to ruin something? I soaked it this evening while hot with PB Blaster. What wrench do you use? My slotted 7/8” socket that I think I bought for another O2 sensor somewhere along the line is too big. 19mm open end that I used just to check for size didn’t seem to fit. Relax, I didn’t try to loosen it with an open end wrench. ; ) The connector did come apart easily though.
Use a 22mm and other then any rust that the PB Blaster should break down the sensor should spin loose pretty easy. I just replaced all 4 of mine. To replace one is not good. O2 sensors made 20 yrs ago are different then the ones how in how fast they respond their readings to the ecu. At the very least replace both upstreams so both banks are tuning more equally. Either way running new and old O2 sensors is not a smart thing to do if you like reliability.
 

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My apologies and thank you. I posted it right before bed because I had to get up early and had a limited window of time. And I was mistaken in thinking the sensor itself unscrewed from the flange. It was dark when I looked at it and I didn’t realize the threaded studs were holding it in.
No worries. I deserved it and the world has become too sensitive anyway. In the meantime now in the light of day I see the problem. One nut was rusted off and gone, while the other rusted partially through and was loose. I’m sure a leak was causing the fault. The sensor came out super easily and the studs seem solid and intact. Probably not even a bad sensor but now the gasket is shot so I need a replacement plus 2 stainless nuts. Should be an easy fix. Not worth waiting for a gasket. Gonna just put a new sensor in.
Hei Erick, replacing O2S will not fix your problem, The problem is your catalytic converter, if you did not want to replace it , you could put extension on your back O2S at that failed bank. dont waist your $$
 

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Your telling Eric not to waste his money but wouldnt it be smart to not spend $3k on new converters right off the hop and maybe try a couple of smaller items first? What if it really is something as simple as a leak that could be fixed by a 50 cent gasket?
 
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‘04 Tundra 4.7 186k in rust belt western PA with original downstream O2 sensors. I think my bank 1 side failed because I’m getting a P0420 bank1 catalyst below threshold but the Cat seems ok. (No loss of power or mpg, downstream side is 20 to 25 degrees hotter on infrared temp scan). My exhaust looks pretty solid even around that area all things considered. My question is how hard are they to remove? Can I expect to ruin something? I soaked it this evening while hot with PB Blaster. What wrench do you use? My slotted 7/8” socket that I think I bought for another O2 sensor somewhere along the line is too big. 19mm open end that I used just to check for size didn’t seem to fit. Relax, I didn’t try to loosen it with an open end wrench. ; ) The connector did come apart easily though.

My wife's Infiniti is very touchy on the fuel quality so I've ran across 02 sensor issues a lot there. She also drives short trips too causing it.

First this is ignore light until you run that truck to 1/4 tank. Then get new gas at a different station. Best from a "Top Tier" station and preferably high grade just so it raises your fuel octane in whats left in the tank. Then get the code cleared and if possible go on a highway road trip for an hour or so to burn off any contaminants on the sensors. Short trips wont burn it off.
If I replaced her sensor everytime it threw a light I'd be doin it a couple times a year. Used to be constant but since only running top tier fuel for the last few yrs it rarely happens since. Hers had a coil fail last time that caused it due to pure gas & worn spark plugs cause it more often from failing to combust good. Fueling a vehicle while a tanker is filling ground tanks causes several fuel related issues too, water/dirt stirs up in stations fuel, regardless it's generally build up on a sensor causing issues.

So far following these few things has worked well for us everytime but once. I have had one sensor that actually failed or simply wouldn't burn off good enough regardless what I tried it threw a code.

My Tundra has over 355k miles and still has its original sensors, had it throw one once. Just dont assume a sensor is bad right away. If it's not bad it's light/code will eventually reset after it burns off but I don't have the patients to wait and I clear mine after refueling with better gas and a good road trip. Not had any luck with bottles of miracle cures myself fwiw.
Just my experiences here.
Take care all!
 

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Use a 22mm and other then any rust that the PB Blaster should break down the sensor should spin loose pretty easy. I just replaced all 4 of mine. To replace one is not good. O2 sensors made 20 yrs ago are different then the ones how in how fast they respond their readings to the ecu. At the very least replace both upstreams so both banks are tuning more equally. Either way running new and old O2 sensors is not a smart thing to do if you like reliability.
So how do people change those upstream sensors? I could barely even get an O2 socket on them, much less have enough room and leverage to break them loose. Looks like I may have to remove the manifolds to get them out. Am I missing something? Mine is an 06 Sequoia with the 4.7.
 

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Like most all Infiniti/Nissan owners we were told by the Nissan dealer our converters were bad already or will be bad very soon everytime a sensor went on it while under warranty.
It's not always the case and it takes a long time to destroy one evidently. Especially as long as people I know that have been driving Nissans around with 02 lights on for many yrs. It was 100k miles ago when we were told ours was bad. That was BS!
My cousins Camry had 02 sensor code on for over 5 yrs and over 100k miles before she gave it to her son. She had me replace all the sensors in that car when she gave it to him and we never replaced it's converters. He's been driving it back & forth to college (out of state highway) for a couple yrs now. It's got over 300k now I know with no issues.
 

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So how do people change those upstream sensors? I could barely even get an O2 socket on them, much less have enough room and leverage to break them loose. Looks like I may have to remove the manifolds to get them out. Am I missing something? Mine is an 06 Sequoia with the 4.7.
Not changed mine but on my old junk GM I had to take engine mount loose and rock engine over to get one out. Manifold crack on these easy. The bolts can break easy on any manifold so I chose the mount besides no gaskets to buy.. sorry not removed on Tundra...
 

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Your telling Eric not to waste his money but wouldnt it be smart to not spend $3k on new converters right off the hop and maybe try a couple of smaller items first? What if it really is something as simple as a leak that could be fixed by a 50 cent gasket?
sorry, you did not get what i told Eric, I did not tell him to spend $3k,
 

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Maybe I didnt get it but you said his 02's are not the problem, its his cats so not sure how else to take that.
 

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Pull the down stream o2s and put red rtv on them install and never have that problem again. Cats may be “inefficient” but still flow. No CEL yet.
 
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