CodePieline didn't allowing to update the stack

[Amanfavas]

Hi Team,
I have created a lambda with the help of cloud formation [template.yml] file, Created one stack also. The lambda is in holding this stack itself.
Then after creating the new codePipeline also. The source is in GitHub, Build provider is AWS code build, Deploying is AWS cloud formation. What I created the previous, the stack only using it. But while running the pipeline stack is getting an error. already exist the lambda in this stack, like that.

I need exact requirements I a created some lambda with help of AWS cloud formation deploy commends,Now I need that lambda in code pipeline itself. From new pipeline I 'll create and update the lambda, what is the solution to without deleting the already created lambda?