P0117 ERROR & P1128 ERROR

Audi A4

Audi A4 Quattro 1.8 liter Turbo
144K miles

I am getting p0117 & p1128 errors. I can look them up in my Bentley manual but I do not know what a P0117 - Engine coolant Temp. Circ Low input or a P1128 - Long Term Fuel Trim mult. Bank 1 System too lean; means or how to go about repairing these errors.
September 22, 2007.

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