EML codes?

[w207]

Hi, Engine man. light came on, a friend plugged it in and came up with this...."confirm manufacturer specific P1131 & P0171" and that's it showing no faults. Does anyone know what these codes are or any info. would be helpful, THANKS!! :?

 

[YOG]

P1131 Lack Of HO2S11 Switch - Sensor Indicates Lean
P0171 System Too Lean (Bank 1)

http://www.svtlightnings.com/scantool/ford%20dtc%20codes.htm" onclick="window.open(this.href);return false;

 

[w207]

Great, thanks for the quick response!!.........that's reminded me that a few months ago the EML came on and showed "o2 censor slow to react" sounds like it could be related?