1996 Dodge Intrepid trouble codes

Code 12 is a battery connection issue. The battery has been disconnected in the last 50 startups.

Code 66 is the pcm not recieving the ccd bus signals. Do you have any other codes?

Both of these sound like a loss of battery voltage to the car. The other option would be a drop in voltage like the alternator quit. If the voltage gets to around 10.5 volts, the electronics quit working. The pcm is generally the last to stop working.