Bought a used Chrysler 300 2009. Owner bought it with remote start, but it had never worked. When he brought it to a dealer they said it'd be over $100 for an "inspection" so he didn't bother.

When I try the remote start, it locks the car. I'm wondering how I can diagnose and repair this myself. I'm thinking it's possibly a PCM issue? The dealer at least confirmed remote start was there when he took it in, it's just not working or something programmed wrong. I'm not too used to mechanics, I just need help to get pointed in the right direction, and I don't want to mess my computer up