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Discussion Starter #1 (Edited)
My first post in this forum. Love this site.

I just recently bought an 2006 Impala SS. I love the car. The check engine light is on with the HO2S errors. The O2 sensor was replaced on it by the car lot I bought the car from. I cleared the codes, but it coded again. There was a hole in the hose from the PCV and I replaced it. Made the car run smoother. Still coded.

I bought a DiabloSports tuner and tuned the car. Runs like a champ, but still get the code. Also faint smell of exhaust. Any ideas what may be causing the issue? Or where to begin diagnosing the issue?

Any information or help would be greatly appreciated.

EDIT: Pic would not upload; here are the codes:

P0030 - HO2S Heater Control Circuit Sensor 1
P0036 - HO2S Heater Control Circuit Bank 1 Sensor 2
P0053 - HO2S Heater Resistance Bank 1 Sensor 1
P0054 - HO2S Heater Resistance Bank 1 Sensor 2
P0135 - HO2S Heater Performance Bank 1 Sensor 1
P0141 - HO2S Heater Circuit Bank 1 Sensor 2
 

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how many miles? If over 100,000 then there is a good chance all the heated (that is what the H stands for) O2 sensors are all bad. But I'm thinking the O2 sensor controller.. If there is one on these things.. hmmm.. Wish we could get those sensors on a scope to test them out to see if they are ok or in fact bad.
 

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Discussion Starter #3
Seems to me that is an awful lot of errors for a replaced sensor. They coded the same way before. The only thing I can attribute it too is maybe it has an aftermarket Cat.
 

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Discussion Starter #5
Well, a year later and the issue is still there. Bank 1 is not showing any voltage on the computer. I replaced the fuses, although the looked ok, and still the same issue. The error codes I listed were there before the sensor replacement. I replaced the catalytic converter, still has the issue. It's effecting the fuel trim.

I'm stumped.
 

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I have NO idea why I could not post with my account, so I created a new one to give the reason there were issues. Come to find out, the O2 sensors, for upstream and downstream are different. I further found out that the people who took it to auction before the dealership bought it replaced the O2's.

There were the codes. Dealership replaced the O2's due to the codes, however the CEL remained lit. So, a buddy of mine with a high end computer tried to track down the issue. O2 upstream was not registering any voltage. Down steam was. We checked the sensor and found it was a downstream sensor in the upstream position. It resolved the upstream issue, however the downstream remained in error.

Now bare in mind that the issue was causing a fuel trim issue. Figuring the upstream may have caused a downstream O2 sensor to malfunction, ordered a new one. One we got to removing the downstream sensor, we found it was an UPSTREAM sensor.

Essentially, they were swapped, and the shop that attempted to repair it replaced them in kind. Once we made sure the O2's were the right ones in the correct location, took care of the issue.

Stupid? Yes. Glad we found it. So there ya have it. Sometimes a garage just does not pay attention.

Problem Solved. I appreciate all the responses and assistance.
 

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Discussion Starter #8
OK, now I get a random P0171 Code every now and again. I reset and it's OK for a couple of days then comes back. Thoughts?
 

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OK, now I get a random P0171 Code every now and again. I reset and it's OK for a couple of days then comes back. Thoughts?
So, from experience, there are a few things that can cause a random P0171.

Most commonly it's gonna be a vacuum leak, a dead / dying MAF sensor or a dead / dying O2 sensor.

Since you've had issues with O2 sensors before, and the problem really only showed up after you've fixed the previous issue, I'd start looking at them first.

It could just be a defective O2 sensor you put in. I changed out one in my buddy's car a few months ago, and everything went well for all of two weeks. Then an intermittent CEL came on, and it was showing an O2 sensor code. Exchanged the defective one and the problem went away and hasn't been back since.

Or, it could even be something as simple as the O2 cable not being fastened correctly and not maintaining a stable connection.

Of course, I could be completely wrong, but I'd look at your O2 sensors again.

Hope this helps some.
 

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Discussion Starter #10
I thought the O2 sensor as well. I went to the local dealer. Great guy at the parts counter and we had a discussion on the issue. He printed out two GM only bulletins. According to the one, it seems as though there are issues with a dirty gas tank. He stated that the issue with that code in particular is a clogged injector on bank one. (Bank one is the front of the car.) He stated the only fuel filter is a screen on the fuel pump which is in the gas tank.

He told me to try a good cleaner, like Seafoam. I went with one less harsh which was the Lucas.

So we'll see. It would be nice to see if anyone had the issue and found out the culprit.
 

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Discussion Starter #11 (Edited)
So, from experience, there are a few things that can cause a random P0171.

Most commonly it's gonna be a vacuum leak, a dead / dying MAF sensor or a dead / dying O2 sensor.

Since you've had issues with O2 sensors before, and the problem really only showed up after you've fixed the previous issue, I'd start looking at them first.

It could just be a defective O2 sensor you put in. I changed out one in my buddy's car a few months ago, and everything went well for all of two weeks. Then an intermittent CEL came on, and it was showing an O2 sensor code. Exchanged the defective one and the problem went away and hasn't been back since.

Or, it could even be something as simple as the O2 cable not being fastened correctly and not maintaining a stable connection.

Of course, I could be completely wrong, but I'd look at your O2 sensors again.

Hope this helps some.

Yes it did, tremendously. Thank you!! I'll try a MAF cleaner as well and see how that does.
 

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You might also want to test (at the rail, with a gauge) your fuel pressure.

From experience, I don't (always) trust the pressure that the ECM reports.
This mostly applies to non-return type systems. If anyone cares, I can go into great detail. ;)
 
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