OBD code P0125

I have a 1997 Yukon with an automatic trans and 5.7,,,it started hard after driving tonight and threw a service engine soon light that I scanned and came up with p0125, which says closed loop fuel control insufficient coolant temp,,,can somebody tell what the likely fix is... I just got the truck but it was running quite well before tonight,,,,153,000 miles,,,,thanks for the help. Oh yeah, I almost forgot while I was driving it before the SES flashed I did get a wired smell in the car, is there a place where a wire could have burned? The temp gauge reads normal, as the car was warmed up, old receipts show a heater control valve changed and flush and fill,,,heater control valve or thermostat possibly?

http://www.obd-codes.com/p0125

The simplest thing to do is to reset the code and see if it comes back.

If the code comes back, the problem is likely going to be the result of the above causes (faulty thermostat, faulty ECT sensor, or a low coolant level).