My CEL has been on for a month. I was getting code P0172 (system to rich, bank 1). Each time I erased the code it would come back after 2trip cycles. I added a bottle of chevron techron to my fuel tank, left the CEL light on then erased thecodeafter I used the full tank. It has been off through many trip cycles and has not returned!

Now my question is, what could have caused the code, and how did the techron help?

Could it have been a bad fuel spray pattern, or a dirty O2 sensor that the techron somehow cleaned?

 

yes and yes. fuel injector was mostly likely not closing properly, and leaking excessive gas into cylinder when it was supposed to be closed. your gas mileage will probably improve too.