The fuel tank sender sends the signal that the gas gauge. The oil pressure gauge sender sends the signal that runs the oil pressure gauge. On the 3800 the part known as the 3 wire coolant temperature sensor is actually a combo unit consisting of a 2 wire CTS (that runs to the computer) and a separate temperature gauge sender, which is wired to the temperature gauge. So none of these senders(sender half of the combo unit) has connection to the computer.
The 3800 computer controls the alternator. The computer thus has a wire that runs to the 'charge' light. This is a simple on/off light.
The voltage portion of the "alternator" gauge just runs off of the cabin voltage.
The 3800 computer also has an output to run the TEMP light. This also is a simple on/off light. The PCM is programmed for the temp that light comes on at.
There is no programming the ECM/PCM has that runs either the stock or Firebird gauges. They simply just run by being electrically connected to their senders.
[This message has been edited by phonedawgz (edited 11-23-2013).]