Auxiliary Air Control Valve (AAC)

The ECU processes signals from monitoring sensors to determine the optimum idle speed under varying engine conditions. The ECU senses engine condition and determines the best idle speed from each cylinder head temperature sensor and the transaxle gear position. It then sends an electrical on-off signal that corresponds to the difference between actual idle speed and optimum idle speed. The AAC valve then regulates the amount of by-passing air by monitoring the length of time that the electrical on signal is presented.