eg here
http://lt1swap.com/2000harness.htm
Blue C1 Pin 42
Empty - Fan 1 Control - This will be empty on 99-2002 harnesses. A pin can be added for electric fan control. Programming will enable the fan control. PCM supplies a GROUND to turn on a relay. If you have two fans, keep reading, pin for fan 2 will be on the RED connector C2. You must wire your fans through a relay.
Green C2 Pin 33
Dk Green - Fan 2 Control - some 99-02 harnesses will have a pin here, this was used for the HVAC Recirculation Door control. The PCM would control the A/C recirculation to help cool the a/c system if it got too hot. In an engine swap, programming can be changed to let this control a second cooling fan. Again, PCM supplies a GROUND to run on a relay. You must wire your fans through a relay.