Hi All, I'm new here but I have read several posts regarding 02 sensor codes. I haven't seen any of the final results as far as what the problem turned out to be. I have a 2005 z71 with a 5.3. It has just developed a terrible miss at times where it feels like half of the engine has shut down.This happens very randomly ,i.e.hot/cold and may occur right from start up or later down the road, or even not at all. The check engine light originally was blinking, then solid, then when the missing would begin it would blink again. If the problem stops ,the blinking stops. The stored codes were p0171 and p0300. I believe these codes are pointing to a lean condition in bank 1. The truck is 4 years old but only has 20,000 miles on it. If anyone has dealt with this particular combination of codes successfully< I'd sure like all the help I can get

 

po171 is left bank o2 sensor is bad,when sensor 1 is bad it goes into closed loop and the computer thinks the motor is lean and sends more fuel to that side(2,4,6 &8cylinders).And thats where your p0300 is coming from(engine misfire).replace the drivers side o2 sensor before the cat and should fix your problem.