Climate Control System Interfaces

SWITCHED HIGH/LOW SIGNALLING







The IHKA/IHKR control module provides two input signals to the Engine Control Module. The two signals are used by the control module for idle stabilization and compressor regulation.




VARYING DUTY CYCLE IHKA INTERFACE

Starting with the 1997 E39 in 1996, a new Climate Control system interface was introduced. The signals KO and AC were combined into one signal providing multiple data through a stepped increase in signal duty cycle. S-KO-REL function is unchanged.







The S-KO input signal to the engine control module signifying IHKA system status. It is a PWM signal with changing duty cycle representing the various system changes.


NOTE: The duty cycle increases from 45 to 90% in steps. At present the engine control module only monitors the difference between 15, 30 and 45% to recognize IHKA system activity. Future engine control systems will utilize the additional load stage settings.