it appears that a lot (or all?) of the P59 OS's have an option for "EV Fan" which i guess really means electro viscous fan clutch. There are also tables for PWM output vs coolant temp which of course do not get used for the traditional relay controlled e fans.

it appears as if this was used on the trailblazers/trailblazer family (envoy, rainier, etc). if you look at the water pumps for these vehicles on rock auto you can clearly see an electrical connector on the fan clutch.

has anyone done any experimenting to see if the PWM output from this could perhaps be suitable for driving PWM e fans?

if no one has proven it cant be done i am going to start looking for an ECM from one of these vehicles and see what the output looks like.