2000 Grand Prix po420 code

Another newbie here! My 2000 GP has a PO420 code popping up. I was told that it is one of a few things - cat converter/ vacuum leak/ o2 sensor or engine misfire. I don't want to start spending money replacing one thing at a time and not get the problem taken care of. The car sort of stalls and acts as if it will cut out and then picks right back up and runs fine. It's not getting very good fuel mileage either. I'd really appreciate any ideas on where to start. Thanks!

Welcome to AF.

How many miles do you have?

The PCM module via the post CAT 02 sensor has detected the converter has less than desirable oxygen storage capability so you have a bad CAT converter.

I have 154,000 miles. This would be why the exhaust is extremely hot when you feel it, right?

That would be one of the symptoms in addition to the DTC and driveability issues you are having. Replace the CAT converter and you should be good to go.

Very cool. I thought that might be my problem with the exhaust being so hot. I imagine that would cause the 02 sensor reading too. I'll check around and see what I'm looking at in price.Thank you much for the info on that. I appreciate it!