Got P0420 and P0430 codes, suggesting the catalytic converter needs to be replaced. Everything I have read suggests the wave form after the cat ( sensor 2) should be a delayed version of before the cat ( sensor 1 ). Is this correct?
What I am seeing is below. This figure is from an OBD software tool. I didn't believe so I double checked by actually connecting to the pins in the ECM as described by the Toyota service manual. I didn't have a scope, but I saw a constant 3.3 volts on sensor 1 and variable voltage on sensor 2 between between 0 and 1 volt. So that seems to conform these graphs.
I'm a novice at auto repair but have some engineering in my past. Can anyone explain this? Is my cat bad? Should I replace it? Thanks from an old retired guy trying to save a buck.