Idle Speed Control (ISC)

PURPOSE
On some models, idle speed is controlled by the Idle Speed Control (ISC) motor and ISC throttle switch.

ISC Motor Operation
The ECM monitors engine load--MAP--and engine speed--rpm--to determine the proper throttle opening.

The ECM then regulates engine speed by transmitting voltage signals to the ISC motor--opening or closing the throttle plates.

ISC Switch Operation
The ISC switch--mounted on the ISC motor housing--is closed when the ISC plunger contacts the throttle lever, and opens as the lever moves away from the plunger.
- When the switch contacts are closed the ISC motor controls idle speed.
- When the switch contacts are open the ISC plunger cannot retract.