2006 chev malibu max code p0128

i have a 2006 chev malibu max and my check engine light came on and the computer from the part store gave a code p0128 wht does this mean. the engine is a v-6 Code P0128; deals with the engine coolant temperature and or the engine coolant temperature sensor circuit.
This code sets when the engine coolant temperature or the computer thinks that the engine temperature has not reached a predetermined temperature in a predetermined time frame.
This could mean that the engine’s thermostat is stuck open or is opening too soon; allowing the engine to run too cold too long?
It may also be a problem with the engine temperature sensor and or its circuit, which maybe signaling the computer the wrong information?
In most cases, when I have seen this code, it’s caused by a bad thermostat.
That being said there are test procedures to confirm which one is the problem.
But with you not likely having a scanner; I would stick a new thermostat in (195 degree); have the code cleared and see if the code returns.
One other thing; regardless of this being a bad thermostat or sensor circuit; you might be using a lot more fuel then need be.
A computer that thinks it’s dealing with a cold engine will add extra fuel because of its programming; a computer “knows” that a cold engine needs extra fuel to run properly.
There’s a lot more to that statement but I’ll leave it there.
Just remember “a cold engine” is a relative term; at 160 degrees, it’ll feel hot to the touch of your hand but an engine that is up to full temperature will run anywhere from 190 to 220 degrees.

I've seen them also with this code where they have taken the thermostat out.
As Dan said you will burn more fuel which can burn out you expensive Catalytic converter
over a long period of time.