I'm about to do the wiring for my electric fans to go along with my 2002 6L engine. I am using a 2002 truck PCM here. I'd like to have two speed fan control using two relays, but I'm not sure that the truck OSes support this. It looks like the f-body PCMs use Blue connector pin 42 for low speed fan control, and Red connector pin 33 for high speed fan control. On the trucks my wiring diagram says that Red 33 is used for A/C Recirculation door control. Frist, I don't see why the PCM would need to control the air recirculation door. Second, is it possible to set up two speed fan control using a truck OS?

I want the PCM to have full control over the fans. I don't want them running above a certain vehicle speed. Any suggestions besides just dealing with the 1 speed fan control? These fans are noisy at full speed!