Quote:
Originally Posted by PhaseP
Before you replace post cat sensor, I suggest check for exhaust leak where the exhaust manifold final pipe connects to the mid pipe of the rest of the exhaust. The bolts and flanges there rust and eventually start to leak. If they are leaking you would find black soot deposits where it leaks. Those two exhaust connections are close to the secondary O2 sensors, so if they leak they effect their readings. Happened to me a few years back, but can't remember what code I had gotten. I didn't not replace the sensor, fixed the leaking connection. Code was only for the secondary sensor though, nothing for first sensor in my case though. Still it is an easy visual check you can do.
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I will probably replace them while I do the testing since I’m already there and will rule out a simple/cheap piece.
The fault strategy I listed does say to check for leaks downstream.
How would a downstream leak after the O2 sensor affect it to the point that it says 0V?