P0137 - O2 Sensor Circuit Low Voltage Bank 1 Sensor 2 - 2009 Pontiac G3 with 80K mile

[SamRus]

Hey guys!

I have 2009 Pontiac G3 with 1.6L engine and about 80K miles that we've had since new. We've been very meticulous about maintenance, and this is only second code we've ever had (First was a year or two ago for a misfire on one of the cylinders due to bad ignition wire and damaged ignition coil).

Yesterday, check engine light came on for a code P0137 - O2 Sensor Circuit Low Voltage Bank 1 Sensor 2.

As far as I understand, this means the Post-Cat O2 sensor is reading lean exhaust gases.
Since Pre-Cat sensor isn't throwing a code, it could be an air leak anywhere in the exhaust stream after pre-cat sensor, or a partial short to ground on the signal wire anywhere between the post-cat O2 sensor and PCM.

It also appears that it's unlikely that the sensor is at fault, because it would throw a different code.

Do you guys have any recommendation on what else to check, or any corrections to my thinking?
Thank you!

[Daox]

Does your exhaust sound louder than normal like it has a hole?

[SamRus]

No, it sounds perfectly fine. I will be raising the car up and listening for any small leaks.
We also live in the area where salt on the roads is not very common.

[Pooh Man]

It is hard pressed to be a leak unless u repeatedly unbolted the manifold. I changed my header and have gotten the same P0137 code as well as P0138 and P0420, long story short it may very well be the o2 sensor because for some reason I don't get consistent OBD codes. Try resetting it and see what comes up, it is my understanding that the 137/138 require a new O2 sensor. Keep us posted. R u losing power??? Could you have banged it up on debris or snow?

[SamRus]

Hey Pooh Man!
No, never unbolted any of the exhaust components, and I'm also thinking that a leak is unlikely, but I'll definitely check it out.
Almost 100% sure I didn't hit anything with the undercarriage to create a leak, because the roads have been clear for a few weeks, and the check engine light just came on yesterday.

Also, it seems to be intermittent. On the way back to work from lunch it went away again. So it seems to come on, and then off.
Stinking O2 sensors for the car cost over $200 at a local parts store, and over $100 online, so I wouldn't want to replace one unless I knew that's the cause of the issue.

It does not seem to impact driveability (acceleration or idle). It shouldn't though, because the downstream O2 sensor is there to monitor efficiency of the cat converter.
I guess another thing I could do, is to swap my upstream sensor with my downstream sensor, clear the codes, and see what happens. If a different code comes up for the upstream sensor, now we know that the problem followed the sensor. If the same code comes up, it's probably something else besides the sensor itself.

Any words of wisdom from you guys?

[Pooh Man]

I too have an 09, I have replaced the second O2 twice by 80K, Try Rockauto, they r cheap and in Madison WI. That's fast shipping to us in IL. The upstream n downstream sensors r different, I don't think they will function properly. Sorry Sam Rus but I wouldn't call anything I say words of wisdom, but thanx anyways. Keep us posted to your solution...

[SamRus]

Thanks guys!
The light went out on Friday, and hasn't come back yet.
So I'll let you know if it comes back and what will fix it.
Thanks again!

[Pooh Man]

Great! I know how good it feels, that damn orange light is annoying!

[larrycheese]

Where is the downstream O2 sensor located on a 2005?