I would do as the others suggested, and unhook MAP, TPS, etc and hope one of the sensors was just shorting the 5 volt reference to ground. You can Ohm out the sensors and connectors. On the connector 5 volt reference at the connector (Power OFF) there should be some resistance to ground. If it is very low resistance, could be a short, it no reading it could mean an open circuit. If you get an open circuit reading, you would want to check the wire from the sensor connector to the computer plug and make sure it is not open. Carefully inspect the computer connector and socket for bent or broken pins. If all the sensors/wiring check out, I would inspect the computer connector solder connections to the computer circuit card for a bad solder joint (I think you mentioned intermittent issues?)

I'll try to look up the codes tomorrow. Too tired today, just got back from the hospital (Wife not feeling well.)