Idle Speed Control (ISC) System

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

The ECU receives signals from such sensors as the coolant temperature sensor and air conditioner 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.