Not sure if this is helpful or just telling you something you already know...but the sampling fan becomes active when the car AWAKES.
The IHKR sampling fan isn't directly on the P-bus which is what activates the SLEEP & AWAKE modes...but those modules that do cause the SLEEP/AWAKE modes are controlled by the GM III...and according to the info below...the GM III is respnsible for putting the K-bus back online when a call is made...and the IHKA control module is on the K-bus:
(see end of 2nd paragraphfor K-bus info)
(you can see where and what bus specific control modules are on and how data moves through the communcation bus)
(low cluster/K,CAN, Diagnostic bus topological chart)
(high cluster & I,K,M,P,CAN, Diagnostic bus topolgy chart)
