coolant temperature sensor GMC sierra 2002?

[betitoal]

I change the "coolant temperature sensor" and the light is turned on, not overheated ..nivel is ok.the gauge is below 170.that it can be?help please.and need take inspeccion sticker,if not TICKET.the code is P0128.
The bad is that nobody wants to erase the codes.

 

[Daniel R]

a p0128 code means the engine is not reaching the correct temperature, it should be 190 deg. what you need is a thermostat, then clear the code with a scanner, some auto parts stores will do that for free.