Step Motor Type ISC Valve

The Step Motor type ISCV is located on the intake air chamber or throttle body. It regulates engine speed by means of a stepper motor and pintle valve which controls the volume of air by-passing the closed throttle valve. The ISCv throttle air by-pass circuit routes intake air past the throttle valve directly to the intake manifold through a variable opening between the pintle valve and its seat.

The valve assembly consists of four electrical stator coils, a magnetic rotor, a valve and valve shaft. The valve shaft is screwed into the rotor so that as the rotor turns, the valve assembly will extend and retract.

Isc CorollaIsc Stepper Motor

The ECU controls movement of the pintle valve by sequentially grounding the four electrical stator coils. Each time current is pulsed through the stator coils, the shaft moves one 44 step." Direction of rotation is reversed by reversing the order with which current is passed through the stator coils.

0 125

Valve Steps

0 125

Valve Steps

The pintle valve has 125 possible positions, from fully retracted (maximum air by-pass) to fully extended (no air by-pass). In the event that the ISCV becomes disconnected or inoperative, its position will become fixed at the step count where it failed. Because the stepper idle speed control motor is capable of controlling large volumes of air, it is used for cold fast idle control and is not used in combination with a mechanical air valve.

Stepper ISC System Applications and Control Parameters

ISC Type/ Engine

Relevant Inputs

Controlled Parameters

Step Motor Type

Engine speed (Ne)

• Warm Curb Idle

Throttle angle (IDL)


Vehicle speed (SPD)

• Cold Fast Idle

• 5M-GE

Coolant temp. (THW)

• 3F-E

Neutral/Start switch (NSW)

• Air Conditioner

• 2VZ-FE


• 3VZ-FE

Ignition switch (STA)

• Electrical Load

Air conditioner clutch (A/C)


Electrical load (ELS)

• Automatic Trans

Battery voltage (+B)

mission Idle-up

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

Don't pay hundreds of dollars to find out what is wrong with your car. This book is dedicated to helping the do it yourself home and independent technician understand and use OBD-II technology to diagnose and repair their own vehicles.

Get My Free Ebook


  • mark young
    How to work stepper motor type isc valve?
    1 year ago
  • anna
    What is stepper motor valve in automobile?
    9 months ago

Post a comment