Idle Speed/Throttle Actuator - Electronic: Description and Operation

CONSTANT IDLE SPEED SYSTEM (CIS)

Constant Idle Speed System:

The constant idle speed system incorporates the following main components: electronic control module (ECM) which operates in conjunction with the Oxygen Sensor Feedback System, air control valve (ACV), throttle switch (TS) and coolant temperature sensor (CTS), Fig. 21.

Fig.22 - Electronic Control Module:

Electronic Control Module

The electrical output from the oxygen sensor is transmitted into the ECM, Fig. 22. The ECM supplies a control current to the frequency valve. The control current incorporates a predetermined frequency and operates by varying the duty cycle. When the oxygen sensor is cold or defective, a fixed control is switched in after approximately 5-10 seconds. The electronic control module is located inside the vehicle at the right hand side in front of the right door.

Air Control Valve

The air control valve bypasses air around the throttle valve. A small electric motor rotates clockwise or counterclockwise, depending on the signal from the electronic control module signal.

Throttle Switch

The throttle actuates a micro switch which controls a circuit in the electronic control unit, when the throttle reaches idle position.

Micro Switch

Fig.23 - Micro Switch:

The micro switch is located at the throttle, Fig. 23. Under normal operating conditions, the electrical transduced vacuum signal is transmitted to the ECM and the circuit when the micro switch is open. With the throttle closed, the circuit is grounded.

Coolant Temperature Sensor

As engine coolant temperature increases, the coolant temperature sensor resistance decreases, giving an analog temperature signal to the electronic control module.