Cruise Control Electronic Control Unit
WARNING: This page is about a different car, the 2002 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.
Cruise control ECU along with input sensors, constantly monitors and compares set speed with actual vehicle speed. When actual vehicle speed is different from preset speed, cruise control ECU activates cruise control actuator to change engine throttle valve position and vehicle speed.
Cruise control ECU includes a self-diagnostic function. If cruise control operation is interrupted by any reason other than driver operation, ECU assumes a malfunction has occurred and sets a corresponding trouble code.