Exactly as the title says!! I got the car about 18 months ago. It's been running perfectly ever since. Apparently the previous owner had the wrong battery in it though (didn't know this until just recently). It died on us about 2 days ago and we got AAA to come out and we get the CORRECT, brand new battery installed.

AAA seemed knowledgeable and mentioned the battery would need to be "programmed" or something to that effect. Not sure.

Now, the next day, the yellow check engine symbol is on. Go to Autozone and it reads code P0420 for the catalytic converter.

I'm assuming changing that faulty battery to the correct one likely triggered this?

Any idea what could be going on? Everywhere I go wants $150 (give or take) just to diagnose what's up even though I have said code.....

For now, the car runs perfectly, and we actually have noticeably saved gas since changing to the correct battery (did a 3 hour trip the day after). Nothing seems amiss at all except that code and the light....

I sure as hell can't afford a new CatCon!!!! :(

Thanks!