Have a code P1811 and it is not on list. What is meaning of code

Question

how do you fix this code on 2003 Impala
3.8 engine

Answer 1

Start by checking/replacing the transmission fluid if it has not been serviced in the last 30k miles, if you still have the problem a you should take it to a  transmission specialist 

if there is hard shifting and there is metal in the transmission, the transmission might be bad.