Just looking for some support here. I got the dreaded P0420 (Bank 1 Catalyst System Efficiency Below Threshold) code. I went ahead and graphed the performance of the O2 sensors, figuring that is the problem. The sensors before the cats ran even with each other for the most part, but the ones after were a different story. I've got the pic below. The part where bank 2 drops off is when I started putting on the gas. As you can see, the bank 1 sensor is all over the place at idle. I seriously doubt I have a cat going bad. Think it's the Bank 1 02 sensor #2?
'90 CRX Si, '98 Explorer V8, '98 Acura ITRally Co-Driver
