I will try to make this short and sweet. Last week I filled up my 2000 Jeep TJ and minutes later the check engine light came on. The code that came back was P0420 Bank 1. The check engine light remained on all week until I got gas today and, boom, the check engine light is gone. I ran my OBD scanner again and it said I had 1 pending code P0420 but was that from the previous issue or is there still an issue? I cleared the code from my OBD, ran a diagnostic again and it came back with no codes. My first question is in regards to the OBD scanner, did I do this correctly or incorrectly? 2nd, why on earth would I have a Catalyst Bank 1 code and then fill up and it goes away??? Anyone care to help? Thank you