There are several factors that affect both number of faults and lines of code, but sometimes in opposite directions.
You can increase the number of lines of code by writing code that is simple, clear, contains self-tests, is well-documented, handles border cases correctly etc, and this will be more code with fewer bugs.
You can increase the number of lines ...
Not an easy question to answer, because LOC can mean many different things:
A large function
A large class (or module in FP)
A large library
A large file
A large code-base
In some of these cases (function and class), LOC can be a proxy for complexity . You can also normalize complexity based on size.
The Software fault prediction metrics: ...