Hi everyone, apologies if this has been asked 1000 times. I have a copy of Torque Lite and have it talking to my bt OBDII adapter.

Question how do I work out which O2 sensor is which. Eg which is precat, post cat and MAF. Reason is I keep getting P0420 code and trying to work out the problem

I have a 2007 Subaru Liberty sedan with EJ253 engine.

Any assistance would be much appreciated.
cheers
Ian

Thanks cooldriver

The only O2 sensor graphs that I can get anything from are:

O2S1Eq – this shows minor fluctuation of the voltage, and

O2 1×2 – this one shows quite a bit of voltage variation and never settles or plateaus .

I assume the “O2 1×2 is the post cat, although not sure what the other is. Also I was assuming that the pre-cat sensor would have been O2 1×1”, although that shows no voltage.