[Ray]

I used a scanner (borrowed) that can read O2 sensors waveform and the bench test using a blow torch the tip of the O2 sensor and monitor the output voltage. Also, I had that rotten smell from the exhaust.

I didn't have any misfire but I had an exhaust manifold leak for awhile that I ignore (fix). Thats the only code (P0420) that ever appears since I own my vehicle.