I've been (increasingly frequently) occasionally getting an O2 high voltage code for Bank 1, sensor 2 on my vehicle - P0138 (2009 toyota matrix, 1.8L). The code would often resolve itself within a drive cycle, so I originally thought it was a bad connection, or dying sensor. As it's increased in frequency, I decided to look more closely, and it does look like even when the sensor is operating correctly, the voltage (and thus lack of O2) is higher than it should be.
I know there is mild damage to the cat - I once limped a few km home on a hard miss on one of the cylinders. A coil died (in hindsight I should have pulled the injector as well) and I was not far from home.
Everything else I can glean from torque appears okay - screenshots included are accelerating (O2 at 0.5v), cruising (O2 at 0.9v - this is the concerning one), and coasting (0.0v).
I don't want to go ahead and replace an expensive cat just because of one symptom, the vehicle is not throwing any other cat codes (no other codes at all)
Is this definitely a cat issue? Could this be as simple as needing an injector cleaning?