Ok Having O2 sensor problems. I replaced my O2 sensor (also only saw one 02 Sensor under there matched the part number on it to before replacing to be sure sense most car parts stores say there are two) about a month ago and drove about 800 miles with no problems no check engine light or anything. Then about two weeks ago my check engine light turned back on and gave me two codes again.

P0036 HO2S Heater Control Circuit (Bank 1 Sensor 2)

P2096 Post Catalyst Fuel Trim System Too Lean Bank 1

Not sure whats going on. What could cause my O2 Sensor to fail again so quickly and Throw this new code now.

Car is 2010 Cobalt SS/TC with 45k miles. Only mods are Full Injen Intake System. Intercooler to Turbo, Turbo to air filter. And everyone that has seen under my car not fellow Cobalt owners seem to think my exhaust is aftermarket but not sure.

Please Help

 

Changed it up a little bit got another code on the scanner so please let me know if someone can help.

 

Was it replaced with an OEM AC Delco O2 sensor?

Is your exhaust blacker than normal or do you have a wierd sounding idle? Could have blow by through the exhaust side turbo seal and its destroying your O2 sensor. I had this happen when I was on the stock turbo.

 

No replaced with a Bosch. AC Delco was way to expensive and only the dealer had it in my area. As for my idle sounds normal does the high idle at start up for about 20 seconds but from what i have understood thats normal. As for exhaust being blacker looks normal to be.

As for the exhaust side turbo seal im guessing that would mean taking apart the turbo to replace that. However, I think I am still under warranty for something like a turbo seal I think. Cuz I have the 5 year 100k warranty at the drive train.

 

The high idle on cold start is the cat warm-up cycle. Completely normal on new cars. As far as those 2 CEL codes, I'm PRETTY (not 100%) sure they're both caused by aftermarket downpipe. I have the same codes as well and I just deleted them from the tune since hours of searching on here didn't find any definite answers.

 

Ok only one thing though I have owned the car for a year now. And didn't start having the cel until about three months ago and if it had an aftermarket downpipe put on would have been before I bought it.

So if it is the downpipe what would cause it to start acting up now and not before.

Could the car have had a tune that it lost somehow? Like battery dying? Or disconnecting the battery for est. 20+ mins???

Thanks again

 

Bringing this post back from the dead hopefully. Still having the same problems haven't done anything hoping that it was an aftermarket down pipe thing.

So new problem that may have to deal with this is sometimes, not every time I will get a backfire when I shift and only when I shift no other time.

Does that help anyone out there please help I have OCD and that check engine light is pissing me off as it has been.

And yes I know the tape trick lol

 

So guess nobody has any advise on this one? I really hate the dealerships 100 dollar fee just to look at it.

 

Just thinking out loud... Which O2 sensor did you replace? Yes, there are two of them. Sensor 2 is the one that's after the cat. Its way way down there under the car.

 

Well I only saw one O2 sensor under there. Also bought the downstream and matched the part numbers. They did match. The one I replaced is closer to the bottom of the engine and the plug for it kind of goes up into the engine bay.

 

Between the engine and the cat? That would be Sensor 1. Sensor 2 is after the cat.

 

Ok just went under there the best I could and the sensor replaced is before the cat. So I do know that should be sensor 1. However, when I was under there when it was replaced I didn't see one after the cat anywhere. It was on a hoist so I could walk under the car so pretty good ability to look.

So if there is a second sensor under there that somehow I missed. Is it going to be before the exhaust curves? Or after closer to the muffler?

 

Just a few inches after the cat. At least that's where mine is, but its an '06. However, I've not seen any OBD2 car that didn't have the downstream sensor within close proximity of the cat.

 

Yeah that's what I don't get. Like I said I matched the part numbers with the downstream sensor I got from autozone with the before cat sensor I replaced and they matched. Also all exhaust parts look stock.

If anybody has the time can you please take pictures of sensor 1 and 2 for me. It would help me out a lot.

I do prefer the LNF exhaust though if possible sense I don't know if it's different.

 

Also the O2 sensor I replaced is on the down pipe if that changes anything.

Also can anyone tell me how to tell if I have an aftermarket down pipe? Because as previously said this can cause these codes I guess.

 

Also I wonder if I am mistaken on what my cat is under there. But if I'm not mistaken the cat is right after the down pipe. Right?

 

If you have an SS/TC the cat is part of the downpipe.

 

Ok so then I did replace the sensor after the cat then. All I gotta say then is that first sensor gotta be way up in there. Now one more question to figure some things out. How do I tell if my down pipe is aftermarket or stock? To find out if these to codes are caused by the down pipe or something else.

 

There are 2 sensors. If I remember properly, one is in the exhaust manifold before the turbo. And this one in the down pipe between the cats.

Factory downpipe here:


The pipe is oriented upside down in this picture. The flex part actually goes up top, coming off the turbo flange.

 

Ok. Making more sense now. And from the looks of the down pipe you got there mine is aftermarket I only have one cat on it. Pretty sure anyway gonna look at it in the morning after work maybe even take a picture.

Trifecta tune can delete those two codes I'm hoping.

Just don't understand what changed between buying it and these codes showing up

 

Oh and my O2 sensor goes into a tube and the tube or whatever goes into the exhaust itself if that makes sense. Anything reason I'm thinking after market.

 

Just to confirm. This is a TC down pipe right?

 

One last thing just to confirm. That's a TC down pipe right? And not a SC?

 

That picture the posted is a stock TC down pipe. Also, that little tube on your down pipe is a defouler, it's meant to place the o2 sensor farther away so it will see less exhaust gas and not throw a code. They are used on aftermarket downpipes with no cat or a high flow cat to trick the ECU into thinking the cat is still there. If your car is not tuned for an aftermarket down pipe it will sometimes still throw a code even with the defouler.

 

Ok now we're getting somewhere. Does that other code make sense for the same situation? The running lean one? And so clearing those codes won't cause problems then just cuz of the down pipe.

Then last question I swear lol. Trifecta tune can that get rid of them for good?