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Discussion Starter #1
Car had been throwing p0050 code at me for a while. Changed o2 sensor with cheap online model. It took away my check engine light, and everything was fine for 2 months. Noticed a rough idle and check engine light on again this week. Checked codes and i'm getting the p0050 again, plus a p0155 and p0150. Any ideas? i'm a bad backyard mechanic at best. But trying to do as much myself as i can...PLEASE HELP! Checked ems fuse and it looks fine. Check engine light didn't come back on after reset for a 30 min drive. As soon as i restarted...check engine light on again.
 

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Discussion Starter #2
These are the codes...sorry I didn't mention above...

P0050 HO2S Heater Circuit Bank 2 Sensor 1
P0150 HO2S Circuit Closed Loop (CL) Performance Bank 2 Sensor 1
P0155 HO2S Heater Performance Bank 2 Sensor 1

is common sense this is the same o2 sensor as all Bank 2 Sensor 1?
 

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08 CTS DI
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Get an original equipment replacement. I know from personal experience to use nothing but OE sensors, especially for O2 sensors. If the codes do not clear up with an original equipment sensor, then you likely have an issue, but having had to return a set of four off brand O2 sensors on a 3.6L before, I would never use an aftermarket O2 sensor on this car.
 

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'12 CTS Performance Sports Wagon AWD
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GM cars generally perform badly on anything but OEM O2 sensors.

Also check connectors and wiring to insure the wire is not burnt or other issues.
 

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Go ahead, blame me. Everybody does 🙄
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'09 CTS DI FE1 Luxury
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Anyone know who makes the sensors for our cars? Denso or Bosch? Someone else?
 

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'09 CTS DI FE1 Luxury
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So which "OEM" sensor should one buy? Personally I would expect any reputable brand to perform flawlessly. AFAIK all narrow band O2 sensors work the same way and vary only in quality of material and construction. I wouldn't experiment with RA's "economy" brands but all the "daily driver" options look good.
 

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Go ahead, blame me. Everybody does 🙄
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So which "OEM" sensor should one buy? Personally I would expect any reputable brand to perform flawlessly. AFAIK all narrow band O2 sensors work the same way and vary only in quality of material and construction. I wouldn't experiment with RA's "economy" brands but all the "daily driver" options look good.
Agreed. I've heard consistently that using off brand O2 sensors cause more problems than money saved.
 

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2009 CTS 3.6L DI rebuilt to FE3 J55 G80 3.42:1
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So which "OEM" sensor should one buy? Personally I would expect any reputable brand to perform flawlessly. AFAIK all narrow band O2 sensors work the same way and vary only in quality of material and construction. I wouldn't experiment with RA's "economy" brands but all the "daily driver" options look good.
We don't have wideband O2 sensors?
 

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08 CTS DI
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So which "OEM" sensor should one buy? Personally I would expect any reputable brand to perform flawlessly. AFAIK all narrow band O2 sensors work the same way and vary only in quality of material and construction. I wouldn't experiment with RA's "economy" brands but all the "daily driver" options look good.
My Mom's LY7 had both Denso and Delphi from the factory, Delphi downstream sensors.

Agreed. I've heard consistently that using off brand O2 sensors cause more problems than money saved.
Yeah, so I replaced all of the O2 sensors on my Mom's car last year as preventive maintenance with the budget sensors from Rockauto. Within a day her car went from no codes to two codes, one addressing O2 correction speed and the other dealing with the heater circuit. RA was good about replacing them with OE sensors and those codes left with the cheap sensors. I matched the originals and interestingly the down streams had different part #s and RA only listed one of the two. Naturally I matched the part #s I took off the car.
 

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'09 CTS DI FE1 Luxury
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Agreed. I've heard consistently that using off brand O2 sensors cause more problems than money saved.
I'm not brave enough to test any of those weirdly named Chinese brands on Amazon. I would trust any of the big name brands. I just wanted to make sure that no one knew of any problems related to quality "oem" aftermarket sensors. I'd hate to have to pay for the GM branded parts when they're made by someone else anyway. With Toyota it's always safe and cheaper to go with Denso rather than Toyota parts and they're always the same part with a different number.

We don't have wideband O2 sensors?
Surprisingly, no. I previously assumed that we did since Toyota and others put them in even their cheapest cars and they are far superior, IMO. I was shocked to learn that GM uses narrow band sensors up and down stream. It may help to explain the poor MPG when everything isn't perfect with these engines. It also means that the down stream sensors may be more important than I previously thought.

My Mom's LY7 had both Denso and Delphi from the factory, Delphi downstream sensors.
Thanks. I suppose if GM mixes them like that, I can too. I'll just stick with good sensors if and when I need them.
 

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2009 CTS 3.6L DI rebuilt to FE3 J55 G80 3.42:1
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Surprisingly, no. I previously assumed that we did since Toyota and others put them in even their cheapest cars and they are far superior, IMO. I was shocked to learn that GM uses narrow band sensors up and down stream. It may help to explain the poor MPG when everything isn't perfect with these engines. It also means that the down stream sensors may be more important than I previously thought.
Interesting. I would have expected these cars to do better on fuel economy, although they can get 25mpg on the highway if babied. But pushing 3,900lbs around with authority in town, that brings down the average. Probably a wideband O2 would help. Maybe the later models with the updated computer get them?
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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To me, downstream sensors are much more important than upstream. OEM, baby!
 

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08 CTS 6.0L/6L80 conversion
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The O2 sensor has a heater built into it to achieve closed loop quicker than just the burnt exhaust gasses passing by it. This should happen in a determined amount of time and the ECM monitors that time. Possible causes could be just a open heater element inside the O2 sensor itself. Other causes could be a blown O2 heater fuse or the wiring controlling the heater circuit. You can check for 12V at the sensor with a simple DVOM. Only the pre cat O2 sensor controls fuel trims the post cat O2 sensor monitors cat efficiency.
 

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Interesting. I would have expected these cars to do better on fuel economy, although they can get 25mpg on the highway if babied. But pushing 3,900lbs around with authority in town, that brings down the average. Probably a wideband O2 would help. Maybe the later models with the updated computer get them?
I'm not sure if or when GM may have adopted wide band sensors but IMO they should. I don't have any firsthand tuning experience with Porsche but my understanding from those who do is that they use widebands and remain in closed loop all the time, letting the PCM control the AFR very precisely under all loads. For some reason Toyota just goes open loop under high loads despite the ability to accurately measure AFR between 12:1 and 20:1. Why GM chose to limit their closed loop metering to a narrow range of 14-15:1 escapes me. I hope it wasn't just to save a few dollars.

To me, downstream sensors are much more important than upstream. OEM, baby!
I feel like there is a joke in there that I'm missing. Big_kid is right, upstreams do the really important work. Downstream O2 sensors can be replaced with a black box or use spacers to compensate for deleted cats with no ill effects.
 
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