Idle Speed Control (ISC) System

Engine idle speed is controlled by the ECU. The ECU contains pre-programmed information which contains specific engine speed values for different engine operating conditions.

The ECU receives signals from such sensors as the coolant temperature sensor (CTS) and air conditioner (A/C) sensor. Using this information, the ECU transmits a command signal to the ISC valve in the throttle body.

The ISC valve opens and closes the idle air by-pass to control the amount of air which by-passes throttle valve. The greater the amount of air which is by-passed around the throttle valve, the greater the engine idle speed.