rrclyoung

2004 F150 Heritage with a 2.4L V6. My SES lamp comes on with codes P0171 and P0174 only when using the temperature control **** on the dash. as long as it stays on cold (Fully CCW) the light stays off, but as soon as I adjust it CW to make the air a bit warmer the light will come on a few days later. It has been my experience that The bank 1 and 2 lean codes are caused by vacuum leaks, so I am assuming that the heater control switch sends vacuum to a heater control valve. Has anyone experienced this before? Does any one know where this elusive heater control valve may be? Any insight or suggestions would be appreciated.