O2 code

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CEL came on the other week in my '99 Camry (with the 2.2L), and as an old VW owner I ignored it, thinking it was the EGR code it had last year. Nope, new one: P0136, for the second O2 sensor. Quick look reveals it could be bad sensor, or an air leak... I could have an air leak, as the flex pipe looks bad--but when I checked I didn't feel any leakage and it certainly doesn't sound loud. I sometimes think I smell exhaust but perhaps it's just oil burning off.

I hooked up Torq and looked. The "O2 1x2" readout appears stuck at zero. As in, zero volts. ? This seems very odd. I cleared the code and have put 50 miles, one cold start and a few hot starts onto it--and the light hasn't come on again. Yet. But the whole drive to work, Torq was indicating zero volts. I'm thinking Torq isn't reading this sensor correctly. It should throw codes and run bad with a seemingly dead O2 output. But all the same, old sensors, code... probably ok to just shotgun replacement?

I did look at the first sensor, and got some plots; I was surprised that it swings when under light load / maintaining highway speed.



To be honest, idle looked the same.


I didn't grab a shot of heavy load though.
 
How many miles on the sensor? The rear sensor can last a LONG time if the engine and cat are in good shape. I don't think an exhaust leak would set a 136 unless it's a big one. If you are going to replace the sensor, you can buy a "universal" from Denso which comes with a splice kit rather than a connector.
That way you don't have to dig around in the interior to find the connector. I used a universal on my son's 95 V6 and it's been fine for 10 years.
 
Any value in replacing both O2 sensors? I should try turning off all displays other than O2 in Torq, see if it updates faster--but it appears like it is swinging as it should be, so I'm thinking the first O2 is still working properly.

I'll check mpg later. I think it's been low 30's for mpg, but I've had the a/c on and no desire to drive for mpg.
 
Originally Posted By: HerrStig
How many miles on the sensor? The rear sensor can last a LONG time if the engine and cat are in good shape. I don't think an exhaust leak would set a 136 unless it's a big one. If you are going to replace the sensor, you can buy a "universal" from Denso which comes with a splice kit rather than a connector.
That way you don't have to dig around in the interior to find the connector. I used a universal on my son's 95 V6 and it's been fine for 10 years.


No idea. I bought it used a year ago, and the owner only had a few service records. I suspect it's original, which would put it around 160kmiles.

I looked briefly at youtube and a vid indicated removing front seat; I suspect that was just to show better how to get to the wiring. I'm not sure if I want to mess with splices in our weather. I'm thinking it might be worth a few bucks to have full replacement (Bosch is $55 on Amazon), as the real work will be in removing the sensor from the exhaust.
 
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I would try replacing the O2 sensor. There may be a wire short to ground somewhere, or an internal sensor short. These things last between 100,000 to 200,000 miles in my experience, so its likely time to replace anyway. Or a bad cat.
 
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Originally Posted By: supton
Originally Posted By: HerrStig
How many miles on the sensor? The rear sensor can last a LONG time if the engine and cat are in good shape. I don't think an exhaust leak would set a 136 unless it's a big one. If you are going to replace the sensor, you can buy a "universal" from Denso which comes with a splice kit rather than a connector.
That way you don't have to dig around in the interior to find the connector. I used a universal on my son's 95 V6 and it's been fine for 10 years.


No idea. I bought it used a year ago, and the owner only had a few service records. I suspect it's original, which would put it around 160kmiles.

I looked briefly at youtube and a vid indicated removing front seat; I suspect that was just to show better how to get to the wiring. I'm not sure if I want to mess with splices in our weather. I'm thinking it might be worth a few bucks to have full replacement (Bosch is $55 on Amazon), as the real work will be in removing the sensor from the exhaust.
good quality crimp splices are supplied with the universal. Nevertheless, I soldered them after crimping. What shape is your "center" pipe in? No point in replacing the sensor and having the pipe fail shortly thereafter. My 99 went through two center pipes in close to 400K.
 
I always thought the post-cat sensor like this is just there to monitor the catalyst, and NOT providing feedback to the engine's fuel injector adjustments.
Yet, when you look on the web for P0136, they do discuss the rich/lean feedback control loop, and maybe they shouldn't mention the control loop when talking about aft 2nd post-cat sensors!

Better hope its not the catalyst gone bad here. O2 sensors are cheap and easy to replace, so could just be that. It was on mine a few years back.
 
Originally Posted By: HerrStig
good quality crimp splices are supplied with the universal. Nevertheless, I soldered them after crimping. What shape is your "center" pipe in? No point in replacing the sensor and having the pipe fail shortly thereafter. My 99 went through two center pipes in close to 400K.


Last I looked, the pipe was ok, flex pipe is on its way out though, looks pretty ratty. Car was in AZ until 5ish years ago? and then lightly driven here? something like that, and the condition of the car confirmed it (no rust and no paint where the sun shines). I need to call around and see if a shop can weld in just the flexpipe, as the "proper" part comes with a cat attached.

Originally Posted By: oil_film_movies
I always thought the post-cat sensor like this is just there to monitor the catalyst, and NOT providing feedback to the engine's fuel injector adjustments.
Yet, when you look on the web for P0136, they do discuss the rich/lean feedback control loop, and maybe they shouldn't mention the control loop when talking about aft 2nd post-cat sensors!

Better hope its not the catalyst gone bad here. O2 sensors are cheap and easy to replace, so could just be that. It was on mine a few years back.


I recall reading once, and haven't found where I read it, that a wideband could be used for first sensor; and a narrowband for post. That way, once the cat was up to temp, the second could be used to calibrate the first. When the mixture is about right, the post should be oscillating about ideal (oscillating quickly or stuck at ideal?). Thus any error in the wideband could be accommodated for.

That is a good point though, if it's been running rich for long perhaps the cat is bad. I'll have to see if it's CA emissions or not.
 
The front sensor, or sensors for each bank in the V6, are part of the feedback loop which the ECU uses to set the mixture. They can get "lazy" and produce stalling problems which don't set a code, or set a misleading one such as "missfire". "Lazy" means they can "stick" after a restart and indicate the last reading before shutoff rather than the current one. They often stick lean when the engine needs a richer mixture after being parked for a while, and it doesn't take long. I believe the latest sensors are more resistant to this. On the 99 I4 the single front sensor is easy to get to.

The rear sensor, BTW, is the one which, as one guy said, "rats you out to the ECU" if the converter isn't cleaning the exhaust properly, but it isn't part of the feedback loop, it causes the ECU to turn on the dreaded check engine light. The front sensor (s) show a changing voltage as the load changes, the rear is supposed to show a steady output. If it starts to mirror the front sensor output it means the converter isn't working properly and the ECU sets the check engine light in response.
 
Originally Posted By: HerrStig
good quality crimp splices are supplied with the universal. Nevertheless, I soldered them after crimping. What shape is your "center" pipe in? No point in replacing the sensor and having the pipe fail shortly thereafter. My 99 went through two center pipes in close to 400K. [/quote]

O2 wires should not be soldered, crimp or supplied connector only, the modern O2 gets its ambient reference by breathing through the wire strands.
 
Splices .

I understand the need to make them weather / water proof .

Either solder them or use good butt crimps with heat shrink over the butt splice . You can even buy butt splices that have the heat shrink made on them .

Were it mine , for that year of car , I would buy an inexpensive O2 sensor & splice it .

Best of luck , :)
Wyr
God bless
 
Originally Posted By: Trav
Originally Posted By: HerrStig
good quality crimp splices are supplied with the universal. Nevertheless, I soldered them after crimping. What shape is your "center" pipe in? No point in replacing the sensor and having the pipe fail shortly thereafter. My 99 went through two center pipes in close to 400K.


O2 wires should not be soldered, crimp or supplied connector only, the modern O2 gets its ambient reference by breathing through the wire strands. [/quote] I guess you better give the benefit of your wisdom to Denso which supplies the splice kit along with the sensor. As I mentioned, I used the Denso supplied kit on an OB Camry ten (10) years ago and and still working fine. If denso supplies it, it ought to be OK, and it is.
 
Originally Posted By: Vikas
Does your code reader shows pass/fail test results? Do you have 4-cyl Camry?


Hrm, Torq won't tell me readiness; I'll have to look later. It did say no pending codes though. Weird. But yes, 4 cylinder / automatic.

Just checked FE. Looks like I was getting 34-35mpg until I got an alignment last month, now I get 32. But I haven't driven for FE lately so it's probably coincidence; and if not, the car wanders less in cross wind so it might just be the way it has to be. [31.8mpg over 19,940 miles for lifetime avg.]
 
Originally Posted By: HerrStig
I guess you better give the benefit of your wisdom to Denso which supplies the splice kit along with the sensor. As I mentioned, I used the Denso supplied kit on an OB Camry ten (10) years ago and and still working fine. If denso supplies it, it ought to be OK, and it is.


Did you even read my post? Nothing wrong with splicing but you should use either the supplied connector or a waterproof crimp with heat shrink tubing. You said this which is totally incorrect.
Quote:
good quality crimp splices are supplied with the universal. Nevertheless, I soldered them after crimping


Some very old style sensors could be soldered because they had a small hole for ambient air but the one in the OP's car and modern ones do not. Soldering them is bad practice.
 
Originally Posted By: Trav
Did you even read my post?


I get that all the time; especially with Donald and JHZR2.
grin2.gif
 
P0136 = bank 1 sensor 2 circuit malfunction. Any time I've had that, replacing the O2 sensor fixed it. Like said above, if all the piping is in good shape it's an easy job and worth trying a new sensor.
 
If you use solder exposing the bare copper on the O2 end right after the solder just a tiny bit will provide a path for the O2.
 
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