I drive a 2004 Impala with just over 100k miles and sometimes it just will not start. All the bells and whistles work fine but it just doesn’t start. The security light flashes 3x and then shows a picture of the battery. I replaced the battery and it seemed fine for a few months, but then did it a few more times. I’ve heard of people spending up to 3k dollars replacing various things, making no difference at all. On most websites everyone seems to thinks it’s the GM Passlock system…any ideas???

There have been quite a few problems with that Passlock thing.  That does not mean that is your problem, but I would suggest that is a good place to look.

Agreed Joe_e