2017 G4 P0137 Code (oxygen sensor / catalyst performance)

[Patrick_Henry]

Hello folks, it's been a while. I've had pretty much trouble free service from my Mirage up until now. I'm getting a P0137 code. I've gotten it a few times now. I'll clear it out and it'll stay off for a little while but it keeps coming back. I thought to myself it's just a bad oxygen sensor. I'll go ahead and order one and install it myself since it's not under warranty anymore. Holy cow, that sensor is between $250 and $350 everywhere I've looked so far. Does anyone know of a cheaper alternative?

[foama]

Beware: The Mirage has one oxygen sensor before the catalyst and another after. They are completely different and thus not interchangable. The top one is capable of differentiating between the exhaust "puffs" and thereby identifies the fuel/air ratio of each cylinder individually.

[klroger]

That is for the Catalyst Monitor. It is down stream from the Cat Converter. Can you see the data from the sensor when the engine is running??? Does it show a signal that looks like the upstream sensor???

[Patrick_Henry]

That is for the Catalyst Monitor. It is down stream from the Cat Converter. Can you see the data from the sensor when the engine is running??? Does it show a signal that looks like the upstream sensor???

Thanks guys, I plugged my scanner back in and looked at the data stream for both sensors. I don't have a lot of experience with them but I believe they're supposed to stay pretty close together. It doesn't look like that's happening to me. I recorded and uploaded it to my youboob channel so ya'll can look at it. I really wish there was a way to delete or bypass it since there's no emissions testing in my area.

https://www.youtube.com/watch?v=fenB0KXybvM

[Fummins]

I don't think I've seen that code yet, you're not the only one though.
https://mirageforum.com/forum/showth...ank-1-sensor-2
https://mirageforum.com/forum/showth...t-Low-Voltage)
https://mirageforum.com/forum/showth...r-Some-queries

[Top_Fuel]

...looked at the data stream for both sensors.
...I believe they're supposed to stay pretty close together.

If the pre/post cat 02 sensor data is essentially the same, that means your catalytic converter isn't working properly. The data from the second O2 sensor should be different from the one in front of the catalytic converter. You're likely to get a P0420 if both sensors are working...but the computer doesn't see a significant difference between the 2 sensors. That P0137 code is telling you that there's something going on with the #2 sensor itself. You can check out THIS video for an overview of how a rear O2 sensor functions.

Here are the 5 pages from the 2015 Mirage service manual explaining how to troubleshoot P0137. There are some specific voltage ranges mentioned in here...so it might help you out with your scan tool monitoring...

[Patrick_Henry]

If the pre/post cat 02 sensor data is essentially the same, that means your catalytic converter isn't working properly. The data from the second O2 sensor should be different from the one in front of the catalytic converter. You're likely to get a P0420 if both sensors are working...but the computer doesn't see a significant difference between the 2 sensors. That P0137 code is telling you that there's something going on with the #2 sensor itself. You can check out THIS video for an overview of how a rear O2 sensor functions.

Here are the 5 pages from the 2015 Mirage service manual explaining how to troubleshoot P0137. There are some specific voltage ranges mentioned in here...so it might help you out with your scan tool monitoring...

Lol, I read through your post so fast that I didn't catch the part about those pages of troubleshooting being in a service manual. I was thinking owners manual. I walked out to my car thinking there's no way they put that info in the owners manual. i was out there scouring the owners manual looking for it. I suppose I need to order a service manual for it. I just haven't needed one until now. So, I got in it and drove approximately 10 miles to the grocery store earlier. I had my scanner hooked up while i drove and then took about a one minute video while I was sitting in the parking lot trying to make sure I stayed within the RPM parameters. I never seen the output voltage drop below 0.6 volts. I unplugged the scanner and did my shopping. I came back out and got in the car to drive back home. I got maybe 2 or 3 miles down the road and the MIL came back on with the same P0137 code. So I have no idea what the deal is with that. I just hate to spend 300 bucks on a new sensor and that not be what the problem is. I found one on Rockauto in the "economy" section for around 50 bucks. I found another one on AliBaba express for around 15 bucks. I've never bought from them before but I'm willing to give it a try for 15 bucks.

https://www.youtube.com/watch?v=q_cCTb7VTHo

[Fummins]

I hate diagnosing O2 sensors. I have to relearn how to do it each time. I've had chit luck with NTK O2 sensors for Gm's lately. 4 sensors in 2 different trucks have been junk, they would intermittently work fine then take a dump causing it to run like pooh. In the end bought some from the dealer.

I just watched part of your video and yikes, go easy on the rev-offs unless you you are trying to clean river water out of it. Seems like you have an intermittent problem. Could check the plug for the rear Sensor, I think it's way down low mounted to a little black plate at the rear of the transmission.

This shows the plug. I broke it a while ago, probably while replacing the engine and ziptied it together. I'm too computer dumb to post the right spot, skip to 6:43


Edit:
I think I fingered it out https://youtu.be/W6eCYLrOAXE?t=403

[Top_Fuel]

If you're short on cash right now, you don't really need to do anything. That post-cat O2 sensor is for emissions monitoring only. It will not impact how the engine is running. So don't feel like you need to get it fixed immediately. You might want to make sure the wires and harness connector look ok for that sensor. Jiggle the wires around a little bit...then cross your fingers and hope the code doesn't come back.

Dang...I just looked at Autozone to price that downstream sensor... Maybe I need to pull one of these the next time I'm at the salvage yard...

[Fummins]

I agree with the above. A piece of electrical tape over the Check engine light seems to be the fix for almost every taxi cab I've seen. Out of sight out of mind!