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2000 Camaro V6 3.8L - P0137 O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2) After Catalytic Converter Replacement

Model: 2000 Camaro Fault Code: P0137 Posted: 2008-09-13 13:42

I own a 2000 Chevrolet Camaro with a 3.8L V6 engine and recently encountered a diagnostic trouble code: P0420 Catalyst System Efficiency Below Threshold (Bank 1). As a result, I had the catalytic converter replaced at a Magnaflow dealership with a universal converter. The new unit is slightly smaller than the original OEM converter. The car now feels more responsive and has a noticeably louder exhaust sound—likely due to a Flowmaster muffler installed in parallel. During installation, I observed that the second oxygen sensor was positioned very close to where welding would occur, but I didn't raise concerns at the time. The technician did not appear to direct any flames toward the sensor during welding. Upon inspection of the original factory catalytic converter, it was severely clogged with melted elements inside. After returning home from the shop, I cleared the P0420 code by disconnecting the battery for a few minutes. Two days later, the Service Engine Soon (SES) light reappeared—but this time with a new code: P0137 Oxygen Sensor Circuit Low Voltage (Bank 1, Sensor 2). I suspect that either the second oxygen sensor was damaged during welding or an incompatible, non-OEM catalytic converter was mistakenly installed. Given that the car runs smoothly and performance has improved, I'm concerned about potential emissions issues. What do you recommend? Should I have the O2 sensor inspected or replaced? How can I verify if the issue is related to the new converter or a damaged sensor? Thanks for any insights!

Related fault codes
P0137
Comments (8)
Anonymous 2008-09-15 08:21

This scenario sounds very plausible—especially with the timing of the code appearing right after catalytic converter installation.

Anonymous 2008-09-15 16:23

A plugged catalyst can overheat and glow cherry red, which may damage the downstream oxygen sensor even if it's not directly exposed to flame.

Anonymous 2008-09-15 18:53

It’s quite coincidental that the P0137 code appeared immediately after replacing the catalytic converter. I was worried about either a damaged O2 sensor or an incorrect installation of a non-compliant converter. By the way, this week the SES light has been off—but only temporarily—so it may be intermittent.

Anonymous 2008-09-16 06:27

Are you saying the code is no longer stored in memory or that the MIL (Malfunction Indicator Lamp) is currently off?

Anonymous 2008-09-16 08:21

Since I had the catalytic converter replaced on Thursday evening, the SES light came back on Saturday afternoon—turned off by Sunday—and reappeared again yesterday (Monday) afternoon. It's still on as of now. I drive a mix of city and highway routes. Could this be due to the second oxygen sensor not adapting to the new catalytic converter’s output? If so, how can I confirm that? Thanks for your help!

Anonymous 2008-09-16 08:54

The issue is likely related to physical damage during removal or welding, poor grounding, a damaged wiring connector, or a blown fuse—before assuming the new converter caused the P0137 code. I’d only consider the converter as a suspect once the O2 sensor has been verified with diagnostic tools.

Anonymous 2008-09-17 11:34

...and you're not ruling out that they might have installed the wrong catalytic converter by mistake? The SES light has remained on since it returned. While the car runs fine and even feels better, I know that the SES code relates to emissions compliance rather than performance. What should I do next? Should I get the O2 sensor tested—how would that be done? Thanks again for all your input! Y2KCamaro

Anonymous 2008-09-17 16:36

The most reliable way to assess both the oxygen sensor and catalytic converter is to use a scan tool to monitor live data from Bank 1 sensors. A faulty converter typically triggers P0420, but if that code has already been cleared or not present, it may point to an O2 sensor issue instead. I recommend returning to the installation shop and clearly explaining that this problem emerged after the catalytic converter was installed. The most likely cause is either overheating from a failed original catalyst or physical damage during installation of the new one.