wrong O2 sensor in 2005 cobalt

Hi Everyone, I have a 2005 Chevy Cobalt 2.2L that had a p0135 code, so I decided to replace the upstream O2 sensor. I did so and cleared the code, but it came back the next day. Problem is, the one I purchased was for a 2.0L engine, which I was able to connect, but the connector, I believe, was reversed so the ground was in the wrong location.
After bringing it to my local Aamco, they said there was a bad wire to the sensor, which was probably the problem to begin with. They repaired the wire and put the correct sensor in, but the light came back on my way home with a p0134 code. At this time, my fear is that by reversing the connector with the first sensor, I damaged the ECM circuit.
Have any of you seen a similar situation? If so, do you think I fried the circuit?
Any info would be greatly appreciated. Thanks.

Hey Kmack, welcome to the forums!

There are some easy checks we can do to point us in the right direction, and figure out if the ECM has a problem. For the record, I kinda doubt your ECM got damaged, but we'll find out.

What kind of tooling do you have available? An incandescent test light and a multimeter (with some sewing t-pins) would allow us to do quite a bit of testing.

Let me know what kind of equipment you have, and we can suggest some checks to do. Doing long posts on my phone sucks, so let me get home tonight and we can go further.

To get a quick idea of where we'really going with this, watch this Scannerdanner video:

Tyler, thank you for your response. The shop found that the replacement sensor was bad also, so once they replaced that, all is good with the check engine light. the other issue i brought the car in for was that the traction control/ abs lights are also on, but they cant get to that until next week, but he told me the code was for the right front speed sensor circuit, and the code was P0045. that code doesn't seem to match what i see online, but i wonder if he is just confusing it with another vehicle, it's a busy place. at any rate, do you have any tips on checking a speed sensor circuit beyond the typical multimeter checks for continuity along the harness?
Again, thank you for the response, this forum seems like it is filled with very knowledgible people willing to help if they can.

This post reminds me of something I saw at a scan tool seminar put on by the local Snap-On dealers. Some of the later model GMs (well later model to me anyway) require a relearn procedure after replacing heated o2s. They have a memory of how long to run the heater to get the sensor active which is updated as the life of the sensor is diminished. So when you install a new sensor, it still wants to crank out the heater like it still has the old tired sensor in it, and burns the girl up.

That would seem to fit this scenario, where they replaced the sensor but didn't do a re-learn, so during my ride home, the sensor was overloaded. They get the car back and the sensor is obviously bad now, so they replace it and do the re-learn, all good.
Being a technician myself ( not automotive), I understand that things go wrong from time to time, it's just frustrating to be on this side.

It could just be coincidence, I'd have to check service info to see if your Cobalt uses the same strategy.
Here's a good free video on a GM that may give you some insight toward diagnosing a wheel speed sensor fault on your car.

This test talking about bias voltage in a abs sensor, question can i do the same test to any sensor that have bias voltage like for example a 02 sensor ?

andyford wrote: This test talking about bias voltage in a abs sensor, question can i do the same test to any sensor that have bias voltage like for example a 02 sensor ?

yes you can! But not all O2 sensors will have a bias

Kmack wrote: Tyler, thank you for your response. The shop found that the replacement sensor was bad also, so once they replaced that, all is good with the check engine light. the other issue i brought the car in for was that the traction control/ abs lights are also on, but they cant get to that until next week, but he told me the code was for the right front speed sensor circuit, and the code was P0045. that code doesn't seem to match what i see online, but i wonder if he is just confusing it with another vehicle, it's a busy place. at any rate, do you have any tips on checking a speed sensor circuit beyond the typical multimeter checks for continuity along the harness?
Again, thank you for the response, this forum seems like it is filled with very knowledgible people willing to help if they can.

Yeah, that code doesn't match up, does it? A RF code would be a C0041. He might have meant a C0045, but that'd be for the the left rear sensor circuit.

That video Noah posted is perfect study material. As you mentioned, the harness is always suspect, especially on a GM. Just this week, I saw an Impala with an open sensor ground wire, broken inside the insulation. Using the bias voltage mentioned in that video helped me find that one pretty quickly.

Just an update, I just replaced the front right wheel bearing due to the fact that when i went to check for voltage at the sensor, the wire broke off in my hand with very little movement. So at that point I had no choice, but luckily the ABS and Traction control lights went away immediatley, so I'm pretty confident that is where the problem was.
But, my daughter was driving the car Sunday and said the check engine light came on again, this time the code is a P0171 bank 1 lean code.
I saw a tip online that said it could be from air getting in at the oil dipstick, and I did find that it wasn't seated, so I re-seated it and cleared the code, but it came back after a day and a half.
Question is, should I expect that this code is related to the original O2 problem? if so , I will bring it back to the same shop, if not, I may go someplace else.
Any thoughts?

I think that if you've had an overall agreeable experience with this shop, you should go back there and have them diagnose this code for you. It may or may not be an oxygen sensor problem, but these people now have a history and familiarity with the car where as a new mechanic would be starting with a blank slate.
Make sense?

Nice find with the wheel bearing/abs connector by the way. A good visual inspection sometimes is all we need when it comes right down to the nuts and bolts of it.