2003 Dodge Caravan. Does not work on Computer and does not start. What is my problem? PCM or BCM? new crak sen?

Parasitic electrical faults drain the battery overnight. They are usually easy to diagnose and inexpensive to fix. They are never in the PCM.

That sounds like just what some shady mechanic told the owner to fish for a big moneymaker. Yep, I would pay 500 bucks for a 2000 Honda Odyssey in the shape that one is - in a heartbeat. Electrical fault is going to be in a component that should turn off with the key out, but doesn't.

Something like a bad relay or solid-state device, like the radio amplifier, a headlight relay, a blown rectifier in the alternator, or something with degraded insulation resistance to ground. Once I find it, it can just disconnect that circuit when I park it, until I get it fixed.