I've got an older PT so I didn't have any trouble, but the newer Chrysler vehicles now use that crazy CANBUS system that controls the power of the radio through the BCM. Your PT may have this type of radio.
Scosche and Peripheral both make an adaptor that takes care of your problems. It's a little black box that should have come with your wire harness.
Looks like this:
Peripheral Electronics
The other possibility is that you have purchased a defective wire harness that is missing the two yellow wires
