P0171 &p0174 1999 1500 5.3l
My service engine soon light used to come and go its self so I let it go. Now it stays on so I hooked my code scanner to it and it read system to lean in bank 1 and 2. I took off the mass air flow sensor and cleaned it. I did my own little smoke test with a cigar, no vacuum leaks. Changed the pcv valve. The code reader tells me that my 02 sensor are in good condition. My fuel pump and fuel filter were replaced 16k miles ago. Truck runs fine, no hesitation or anything. Just bugs me that the light is on. OBD codes alsot says it could be an exhaust leak between the 02 sensor and the engine but my exhaust manifold and gasket was replaced 16k miles ago when I bought the truck. I'm running out of things it could be. Please help! Thanks






