Fault P0171

[UStoyota]

I own a Corolla (year 2000 model). I had P0171 fault few months ago. After internet search and discussion with my mechanic, I added one bottle of fuel injector cleaner available in Walmart. The check engine light (CEL) disappeared very soon. It however came back after few days. I repeated the same few times after each fueling. I also started adding mid-grade gas instead of regular grade. Further, one of my friends told me that I should run the car on highway after each time I add injector cleaner, to force the deposition to dissove faster. I was mainly using the city roads as my work place was very close to my home. So, I started taking my my car to highway more often specially after adding the injector cleaner. Now it has been over two months that CEL didn't reapear. I am very happy with all the efforts and analysis I did on this subject and saved $500-1000 on repair. Hope my experience will help other people also.