Car ran fine till last night when a "Check Transmission" message appeared on the dash. Then this morning it was hard to start and idled poorly, wouldn't shift gears properly and the check engine light was on. Auto parts store checked for error codes and said that over 50 codes were reported across every system. Took it to a local auto shop for a diagnostic and after going through it they said it looked like a short in a wiring harness somewhere. They said that tracking it down was beyond them and to take it to a dealer or electrical shop. I asked if it could be the PCM and they said it's unlikely that a bad PCM would throw so many codes.
I'm hoping that somebody out there might have some suggestions on where to start looking for what is causing this.