Throttle Full Close Switch: Description and Operation

Idle Contact Switch:

The idle contact switch is an integral part of the Idle Speed Control (ISC) actuator, and provides an input voltage signal to the engine controller. When the engine controller sees this input it indicates that one of two situations are occurring. Either the vehicle is experiencing a deceleration condition or it is stopped at an idle, the engine controller uses other inputs to determine which situation exist.

DECELERATION

If the engine controller receives a signal from the idle contact switch (indicating a closed throttle) and it also senses that the vehicle is rolling (from the vehicle distance (speed) sensor) and the MAP sensor value indicates a high vacuum condition, then the engine controller knows that the vehicle is decelerating. In this situation, the engine controller would use the MAP signals to determine the appropriate position of the ISC actuator, and it would use the distributor pick-up signal to to indicate the engine speed so that the injector pulse width and ignition timing can be controlled to eliminate an excessively rich condition.


STOPPED AT AN IDLE

If the engine controller receives a signal from the idle contact switch (indicating a closed throttle) and it also senses that the vehicle is not rolling (no output from the vehicle distance (speed) sensor), then it knows that the vehicle is stopped at idle. In this situation, the engine controller would send signals to position the ISC actuator to achieve the specified idle speed.