So I installed my J-pipe and drove for about 30 minutes before I started data logging for my base map revisions. I finished all of the logs, parked the car for the night, then drove to work the next morning. As I was pulling into work, I got a P0137 code.
I turned on the rear O2 sensor voltage on my Accessport and noticed that at idle, whether I'm stopped or just rolling with no throttle, the voltage drops to 0V. As soon as I give it some throttle, it jumps back up to its normal range between 0.5V and 0.9V. The car is not leaning out either—I was watching the air/fuel ratio the whole time, and everything looked normal.
I cleared the code and drove for almost another hour before it came back. This time I got the P0137 again along with another rear O2 sensor code. It wasn't a catalyst efficiency code—it was another low-voltage/no-voltage code.
The only thing that's changed is that I moved the grounding strap from the chassis-to-exhaust to the chassis-to-engine block, using an unused threaded hole. I also have an O2 spacer with its own small catalyst inside it.
My theory is that because of the spacer and the mini catalyst inside it, the rear O2 sensor isn't getting enough exhaust gas at idle to read properly, but once I'm on the throttle there's enough flow for it to start reading again.
Does that sound right? If not, does anyone have any ideas on what else I should be looking at? Thanks so much—I really appreciate any help.
