Timing chain warning or alert on dashboard
will a nissan sentra 2008 give me a code or light on my dashboard screen if i
need to change the timing chain
No, there's no such thing. By the time u get some type of warning caused by a bad timing chain, it will be too late.
To maximize timing chain life, it is very critical to do oil change on time.
It is possible you could get a code related to the cam timing being off but there is no "sensor" for the cam chain.
Good lord I love you F_O_R, there is no timing chain sensor but a cam sensor. However they do regularly need tensioner replacement.