So after a long road trip to San Jose and back to Arizona I refueled to full tank and after a few miles of driving my cel came on. I went to my mechanic and he says my engine is running rich and that I had put bad gas into my truck, so after running it till the low fuel light came on I filled back up with chevron and I disconnected the battery terminals and it resetted the code and stayed off for about 100 miles now it's back. The truck runs fine, no rough idle or loss in power. My mechanic tried cleaning the maf sensor but no luck. Also the air filter is clean and I just had a oil change. What could be causing this? Do I have to drive longer so the computer can relearn the right fuel? I have no clue on what the alcohol percentage was or the fuel trim specs, but my mechanic also did a fuel trim reset and the light came back on immediately with no delay
About the truck it's a 2011 Silverado 1500 4x4 5.3l with no mods but a 2 inch lift.

 

is it a flex fuel vehicle? Check the flex fuel sensor reading as it may be askew. if you aren't using ethanol fuels and the reading is high, it will run rich. reset the flex fuel sensor with a scan tool.