01 malibu coolant temp sensor

i have an 01 chevy malibu with 3l v6. I have replaced the coolant temp sensor, but the check engine light keeps coming on and giving the same code. after awhile it will go off and everything is fine.

what code?

does the gauge work. if the gauge works and the doesnt and the does,

change the t-stat and it should fix it, did to mine