The PCM (Powertrain Control Module) is located under the Air Cleaner Box (Passenger Front Corner under the hood). You need to remove the hoses & filter to the box and unbolt it to lift it out. The PCM sits beneath it like the following Illistration:
Remove the stud bolt and the push pin attaching the PCM to the body. The push pin has a center lock. Pull the center lock up to remove the push pin.
The 60way connector has a bolt on it which you loosen off to pull the connector.. clean it and re-insert it.. tighten only to 35 inch lbs. On the same side of the car up on the firewall you will notice a group f onnection there.. clean all of them also.
Code 12 is normal... code 27 in an open in an injector circuit.. usually a bad connection in wiring is the cause.
Cheers