Impreza Coupe FWD F4-1820cc 1.8L SOHC (1995)
Idle Speed Control Solenoid: Description and Operation
PURPOSE/OPERATION
The idle speed control (ISC) solenoid controls the amount of air allowed to bypass the throttle plate. Using this solenoid the ECM is able to
accurately maintain correct idle speed. The ISC valve utilizes a duty solenoid design so that the amount of valve lift is determined by the operating
frequency. Whenever the engine is running, the ISC solenoid functions. The ECM uses a duty-cycle pulse to determine the rate of air flow through
the solenoid. The ECM uses the following input signals to determine ISC duty ratio:
^
Crankshaft position sensor
^
Camshaft position sensor
^
Throttle position sensor
^
Engine coolant temperature sensor
^
Vehicle speed sensor 2
^
Ignition switch
^
A/C switch
^
Neutral position switch (M/T only)
^
Inhibitor switch (A/T only)
