I don't know how different the 3100 is from the 3.1 or the 2.8 in this area, but if no one else answers perhaps this will help. On the 2.8, the D1 Fan Request wire goes to the Fan Temperature Switch located in the photo below:
The C2 Temp Gauge sender feed and the D3 Coolant Warning Lamp feed go to a common sender located on the aft cylinder head under the coil. The easiest way to know which wire goes to which terminal is by checking the resistance between one of the sender pins and ground. If you get infinite ohms, then the warning lamp wire gets connected to that pin, and if you get a resistance in the 1300-1500 ohm range at ambient temp, then the gauge wire gets connected to that pin.
