I have the weirdest problem with an '07 G35S Sedan I recently picked up for my wife. We bought it knowing the check engine light was on. I scanned it and got a P0057 code. So, I reset the light and the next day it came back on. So I ordered a new O2 sensor. When I went to change it out, I noticed the old one was unplugged and the wire for it was zipped tied up. It looked like it was unplugged on purpose, which was weird. So I took it out, and installed the new one anyways. After I reset the light and started the car, it idled good and seemed ready to go, but when I went to take off, it acted like it was in a limp mode and wouldn't accelerate past 1500 rpms. So I scanned again, and there were no codes and no dash lights on. Well, at the point I went ahead and unplugged the new O2 sensor. All of the sudden the card ran fine and would run normal again. I scanned again, and got a pending P0057. So I am stumped as to why the rear O2 sensor would cause this.

 

I am stumped! Any help?

 

Clogged/defective catalytic converters perhaps?

Telcoman

 

I was sort of thinking the same thing, but the car runs perfect when the oxygen sensor electrical connector is unplugged! I even took out an O2 sensor and had it dangling in the air, just plugged in, and the wouldn't rev. The cats aren't overheating or making noises, either. Does the wiring to the rear O2 sensors connect to the throttle body somehow?

 

Has the rear O2 sensor heater wires ever made a common short somewhere?